U.S. patent application number 13/945793 was filed with the patent office on 2015-01-22 for gas turbine emissions control system and method.
The applicant listed for this patent is General Electric Company. Invention is credited to Timothy Andrew Healy, Achalesh Kumar Pandey.
Application Number | 20150020530 13/945793 |
Document ID | / |
Family ID | 51167738 |
Filed Date | 2015-01-22 |
United States Patent
Application |
20150020530 |
Kind Code |
A1 |
Pandey; Achalesh Kumar ; et
al. |
January 22, 2015 |
GAS TURBINE EMISSIONS CONTROL SYSTEM AND METHOD
Abstract
Embodiments of the present disclosure are directed towards a
system including a gas turbine engine, a selective catalytic
reduction system, and a control system configured to regulate
operation of the selective catalytic reduction system based at
least partially on preset variations in an emissions compound of
exhaust gases produced by the gas turbine engine.
Inventors: |
Pandey; Achalesh Kumar;
(Greenville, SC) ; Healy; Timothy Andrew;
(Greenville, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Family ID: |
51167738 |
Appl. No.: |
13/945793 |
Filed: |
July 18, 2013 |
Current U.S.
Class: |
60/772 ;
60/39.5 |
Current CPC
Class: |
B01D 53/8625 20130101;
B01D 53/8696 20130101; F01N 2610/02 20130101; F05D 2270/331
20130101; Y02T 10/12 20130101; F02C 3/30 20130101; F05D 2270/082
20130101; Y02T 50/671 20130101; F01N 3/208 20130101; Y02T 50/677
20130101; Y02T 50/60 20130101; Y02T 10/24 20130101 |
Class at
Publication: |
60/772 ;
60/39.5 |
International
Class: |
F01N 3/20 20060101
F01N003/20 |
Claims
1. A system, comprising: a gas turbine engine; a selective
catalytic reduction system; and a control system configured to
regulate operation of the selective catalytic reduction system
based at least partially on preset variations in an emissions
compound of exhaust gases produced by the gas turbine engine.
2. The system of claim 1, wherein the preset variations are
scheduled variations, and the scheduled variations include a first
level of the emissions compound for a first period of time and a
second level of the emissions compound for a second period of
time.
3. The system of claim 1, wherein the control system is configured
to regulate an amount of a reductant injected into the selective
catalytic reduction system based at least partially on the preset
variations in the emissions compound of the exhaust gases produced
by the gas turbine engine.
4. The system of claim 3, wherein the reductant is ammonia.
5. The system of claim 1, wherein the control system is further
configured to regulate operation of the selective catalytic
reduction system based at least partially on a permitted level of
the emissions compound in processed exhaust gases produced by the
selective catalytic reduction system.
6. The system of claim 1, wherein the controller comprises a gas
turbine engine controller configured to achieve the preset
variations in the emissions compound of exhaust gases produced by
the gas turbine engine by regulating one or more operating
parameters of the gas turbine engine.
7. The system of claim 6, wherein the one or more operating
parameters comprises a fuel split of a combustor of the gas turbine
engine, a water injection of the combustor, a flame temperature of
the combustor, an air-fuel ratio of the combustor, or a combination
thereof.
8. A method of operating a turbine system, comprising: operating a
gas turbine engine of the turbine system at less than full load;
increasing an emissions compound in an exhaust gas produced by the
gas turbine engine; utilizing available capacity of a selective
catalytic reduction system of the turbine system to reduce the
emissions compound in the exhaust gas to produce a processed
exhaust gas.
9. The method of claim 8, wherein increasing the emissions compound
in the exhaust gas comprises reducing water or steam injection into
a combustor of the gas turbine engine.
10. The method of claim 8, wherein increasing the emissions
compound in the exhaust gas comprises increasing a flame
temperature within a combustor of the gas turbine engine.
11. The method of claim 8, wherein increasing the emissions
compound in the exhaust gas comprises adjusting a fuel split into a
combustor of the gas turbine engine or adjusting a fuel-air ratio
of the combustor.
12. The method of claim 8, wherein utilizing available capacity of
the selective catalytic reduction system comprises regulating
injection of a reductant into the selective catalytic reduction
system.
13. The system of claim 12, comprising regulating injection of the
reductant into the selective catalytic reduction system based at
least partially on a measured amount of unreacted reductant in the
selective catalytic reduction system.
14. The system of claim 12, comprising regulating injection of the
reductant into the selective catalytic reduction system based at
least partially on a measurement of the emissions compound in the
processed exhaust gas.
15. A method of operating a turbine system, comprising: scheduling
variations in a first amount of an emissions compound in exhaust
gas produced by a gas turbine engine of the turbine system;
regulating operation of a selective catalytic reduction system of
the turbine system to achieve a second amount of the emissions
compound in a processed exhaust gas produced by the selective
catalytic reduction system based at least partially on the
variations in the first amount of the emissions compound in an
exhaust gas produced by the gas turbine engine of the turbine
system.
16. The method of claim 15, wherein regulating operation of the
selective catalytic reduction system of the turbine system to
achieve a second amount of the emissions compound in the processed
exhaust gas produced by the selective catalytic reduction system
comprises regulating a third amount of a reductant injected into
the selective catalytic reduction system.
17. The method of claim 16, wherein regulating the third amount of
the reductant injected into the selective catalytic reduction
system comprises measuring a fourth amount of unreacted reductant
in the selective catalytic reduction system and adjusting the third
amount based on the fourth amount.
18. The method of claim 15, comprising adjusting one or more
operating parameters of the gas turbine engine to achieve the
variations in the first amount of the emissions compound in the
exhaust gas produced by the gas turbine engine of the turbine
system.
19. The method of claim 18, wherein adjusting one or more operating
parameters of the gas turbine engine to achieve the variations in
the first amount of the emissions compound in the exhaust gas
produced by the gas turbine engine of the turbine system comprises
reducing a water or steam injection into a combustor of the gas
turbine engine.
20. The method of claim 18, wherein adjusting one or more operating
parameters of the gas turbine engine to achieve the variations in
the first amount of the emissions compound in the exhaust gas
produced by the gas turbine engine of the turbine system comprises
regulating combustion fuel splits of a combustor of the gas turbine
engine.
Description
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to turbine
systems and, more specifically, to systems and methods for
regulating emissions produced by such turbine systems.
[0002] Gas turbine systems typically include at least one gas
turbine engine having a compressor, a combustor, and a turbine. The
combustor is configured to combust a mixture of fuel and compressed
air to generate hot combustion gases, which, in turn, drive blades
of the turbine. Exhaust gas produced by the gas turbine engine may
include certain byproducts, such as nitrogen oxides (NO.sub.x),
sulfur oxides (SO.sub.x), carbon oxides (CO.sub.x), and unburned
hydrocarbons. In general, it is desirable to eliminate or
substantially reduce the amount of such byproducts in the exhaust
gas prior to releasing the exhaust gas into the atmosphere.
BRIEF DESCRIPTION OF THE INVENTION
[0003] Certain embodiments commensurate in scope with the
originally claimed invention are summarized below. These
embodiments are not intended to limit the scope of the claimed
invention, but rather these embodiments are intended only to
provide a brief summary of possible forms of the invention. Indeed,
the invention may encompass a variety of forms that may be similar
to or different from the embodiments set forth below.
[0004] In a first embodiment, a system includes a gas turbine
engine, a selective catalytic reduction system, and a control
system configured to regulate operation of the selective catalytic
reduction system based at least partially on preset variations in
an emissions compound of exhaust gases produced by the gas turbine
engine.
[0005] In a second embodiment, a method for operating a turbine
system includes operating a gas turbine engine of the turbine
system at less than full load, increasing a first level of an
emissions compound in exhaust gas produced by the gas turbine
engine, and utilizing available capacity of a selective catalytic
reduction system of the turbine system to reduce a second level of
the emissions compound in processed exhaust gas produced by the
turbine system.
[0006] In a third embodiment, a method of operating a turbine
system includes scheduling variations in a first amount of an
emissions compound in exhaust gas produced by a gas turbine engine
of the turbine system and regulating operation of a selective
catalytic reduction system of the turbine system to achieve a
second amount of the emissions compound in processed exhaust gas
produced by the selective catalytic reduction system based at least
partially on the variations in the first amount of the emissions
compound in exhaust gas produced by the gas turbine engine of the
turbine system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] 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:
[0008] FIG. 1 is a block diagram of a turbine system that includes
a system for controlling emissions of the turbine system, in
accordance with embodiments of the present disclosure;
[0009] FIG. 2 is a flow chart of a method for controlling emissions
of the turbine system of FIG. 1; and
[0010] FIG. 3 is a flow chart of a method for controlling emissions
of the turbine system of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0011] One or more specific embodiments of the present invention
will be described below. In an effort to provide a concise
description of these embodiments, all features of an actual
implementation may not be described in the specification. It should
be appreciated that in the development of any such actual
implementation, as in any engineering or design project, numerous
implementation-specific decisions must be made to achieve the
developers' specific goals, such as compliance with system-related
and business-related constraints, which may vary from one
implementation to another. Moreover, it should be appreciated that
such a development effort might be complex and time consuming, but
would nevertheless be a routine undertaking of design, fabrication,
and manufacture for those of ordinary skill having the benefit of
this disclosure.
[0012] When introducing elements of various embodiments of the
present invention, the articles "a," "an," "the," and "said" are
intended to mean that there are one or more of the elements. The
terms "comprising," "including," and "having" are intended to be
inclusive and mean that there may be additional elements other than
the listed elements.
[0013] Embodiments of the present invention generally relate to
techniques for controlling emissions of a gas turbine system. For
instance, in gas turbine systems, one or more gas turbine engines
may combust a fuel to produce combustion gases for driving one or
more turbine stages, each having a plurality of blades. Depending
on the type of fuel that is combusted, exhaust emissions resulting
from the combustion process may include nitrogen oxides (NO.sub.x),
sulfur oxides (SO.sub.x), carbon oxides (CO.sub.x), and unburned
hydrocarbons. Often, the composition of exhaust gases released by
gas turbine systems, such as a gas turbine power generation plant,
is subject to stringent regulatory requirements. By way of example
only, regulations may require that the NO.sub.x composition of the
exhaust gas that is released into the atmosphere is no greater than
a threshold level, such as 3 parts-per-million (ppm).
[0014] One technique for removing or reducing the amount of
NO.sub.x in an exhaust gas stream is by Selective Catalytic
Reduction (SCR). In an SCR process, a reductant, such as ammonia
(NH.sub.3) is injected into the exhaust gas stream and reacts with
the NO.sub.x to produce nitrogen (N.sub.2) and water (H.sub.2O).
The effectiveness of the SCR process may be at least partially
dependent upon the amount of reductant injected into the exhaust
gas stream. However, when reductant is over-injected into the
exhaust gas stream, the excess reductant may not react with
NO.sub.x. As a result, an amount of reductant may "slip" or pass
through the SCR process unreacted.
[0015] Another technique for removing or reducing the amount of
NO.sub.x (or other emissions compound) in an exhaust gas stream is
by regulating operation of the gas turbine system. For example,
fuel system operation (e.g., adjustment to fuel-air ratio, fuel
splits, etc.) may be regulated to maintain low flame temperatures
within the combustor of the gas turbine system and thereby reduce
NO.sub.x emission levels. For further example, injecting water or
steam into a combustor of the gas turbine system may reduce
NO.sub.x emission levels. However, water or steam injection can
increase combustion dynamics (e.g., acoustic and/or pressure
oscillations) within the turbine system. As a result, it may be
desirable to monitor and/or regulate the amount of water or steam
injected into the combustor of the turbine system.
[0016] As such, in accordance with embodiments of the present
invention, a turbine system, such as a simple cycle heavy-duty gas
turbine system or an aircraft engine derivative combustion system,
may include a control system configured to regulate and coordinate
various emissions control techniques of a gas turbine system (e.g.,
fuel/air ratio, flame temperature, steam injection, water
injection, fuel composition, etc.) and a selective catalytic
reduction system (e.g., in an exhaust section) to achieve a desired
quality of emissions (e.g., stack emissions) produced by the
turbine system. For instance, as will be described further below,
the control system may be configured to utilize available NO.sub.x
reduction capacity of the SCR system to reduce NO.sub.x emission
levels, while enabling reduced usage of emissions control measures
in the gas turbine system. In this manner, fuel system operation
may be adjusted (e.g., fuel/air ratio may be increased or
decreased), steam or water injection may be reduced, or other
operating parameters of the gas turbine system may be adjusted or
improved to reduce combustion dynamics (e.g., acoustic and/or
pressure oscillations) and thereby reduce mechanical and thermal
fatigue to combustor and/or turbine hardware. Additionally,
performance, power output, and efficiency of the turbine system may
be improved.
[0017] In one embodiment, variations in the amount of NO.sub.x
produced by the gas turbine of the gas turbine system (e.g.,
variations in the amount of NO.sub.x in the exhaust gases sent to
the SCR system) may be preset or scheduled. For example, gas
turbine NO.sub.x emissions may be scheduled as a function of gas
turbine load. As such, a controller of the SCR system may be
configured to inject an appropriate amount of reductant (e.g.,
based on the amount of NO.sub.x in the exhaust gases produced by
the gas turbine) into the SCR system to maintain emissions levels
(e.g., NO.sub.x levels) below a threshold level in the gas turbine
system emissions (e.g., stack emissions). In another embodiment,
the amount of reductant "slip" in the SCR system (e.g., amount of
unreacted reductant) and the amount of NO.sub.x in the gas turbine
system emissions (e.g., stack emissions) may be simultaneously
controlled to decrease emissions control measures in the gas
turbine engine causing an increase of NO.sub.x in the exhaust gases
entering the SCR system, while still maintaining emissions levels
(e.g., stack NO.sub.x levels) below a desired or threshold level in
the SCR system. To this end, one or more gas turbine (e.g.,
combustion) operating parameters may be adjusted to reduce
emissions control measures in the combustors, which may reduce the
amount of combustion dynamics produced during gas turbine operation
and/or improve power output, performance, efficiency, etc. of the
turbine system, as discussed below. While the embodiments discussed
below are described in a NO.sub.x reduction context, it will be
appreciated that the disclosed techniques may be utilized with the
reduction of other emissions compounds (e.g., CO) as well.
Additionally, in certain embodiments, a level of a first emissions
compound (e.g., NO.sub.x) may be increased, thereby causing a
decrease in a level of a second emissions compound (e.g., CO). For
example, in the manner described below, as NO.sub.x emissions
levels are increased in the gas turbine engine, CO levels may be
decreased in the gas turbine engine.
[0018] With the foregoing in mind, FIG. 1 is a block diagram of an
exemplary turbine system 10 that includes a gas turbine engine 12
and an exhaust processing system 14. In certain embodiments, the
turbine system 10 may be a power generation system. The turbine
system 10 may combust liquid or gas fuel, such as natural gas
and/or a hydrogen-rich synthetic gas, to generate hot combustion
gases to drive the turbine system 10.
[0019] As shown, the gas turbine engine 12 includes an air intake
section 16, a compressor 18, a combustor section 20, and a turbine
22. The turbine 20 may be drivingly coupled to the compressor 18
via a shaft. In operation, air enters the turbine engine 12 through
the air intake section 16 (indicated by the arrows 17) and is
pressurized in the compressor 18. The compressor 18 may include a
plurality of compressor blades coupled to the shaft. The rotation
of the shaft causes rotation of the compressor blades, thereby
drawing air into the compressor 18 and compressing the air prior to
entry into the combustor section 20.
[0020] The combustor section 20 may include one or more combustors.
In one embodiment, a plurality of combustors may be disposed at
multiple circumferential positions in a generally circular or
annular configuration about the shaft. As compressed air exits the
compressor 18 and enters the combustor section 20, the compressed
air may be mixed with fuel 19 for combustion within the
combustor(s). For example, the combustor(s) may include one or more
fuel nozzles that inject a fuel-air mixture into the combustor(s)
in a suitable ratio for combustion, emissions control, fuel
consumption, power output, and so forth. The combustion of the air
and fuel generates hot pressurized exhaust gases, which may then be
utilized to drive one or more turbine stages (each having a
plurality of turbine blades) within the turbine 22. In operation,
the combustion gases flowing into and through the turbine 22 flow
against and between the turbine blades, thereby driving the turbine
blades and, thus, the shaft into rotation to drive a load, such as
an electrical generator in a power plant. As discussed above, the
rotation of the shaft also causes blades within the compressor 18
to draw in and pressurize the air received by the intake 16.
[0021] The combustion gases that flow through the turbine 22 may
exit the downstream end 24 of the turbine 22 as a stream of exhaust
gas 26. The exhaust gas stream 26 may continue to flow in the
downstream direction 27 towards the exhaust processing system 14.
The exhaust processing system 14 may include a high pressure (HP)
air-to-steam heat exchanger 31, an intermediate pressure (IP)
air-to-steam heat exchanger 33, and a low pressure (LP)
air-to-steam heat exchanger 35 for transferring thermal energy from
the exhaust gas 26 to other systems (e.g., steam turbines). Other
embodiments may include some or none of the heat exchangers 31, 33,
and 35. The downstream end 24 of the turbine 22 may be fluidly
coupled to an SCR system 30 of the exhaust processing system 14. As
discussed above, as a result of the combustion process, the exhaust
gas 26 may include certain byproducts, such as nitrogen oxides
(NO.sub.x), sulfur oxides (SO.sub.x), carbon oxides (CO.sub.x), and
unburned hydrocarbons. Due to certain regulatory requirements, the
exhaust processing system 14 may be employed to reduce or
substantially minimize the concentration of such byproducts prior
to releasing the exhaust gas stream into the atmosphere. As will be
appreciated, the SCR system 30 may be designed or sized based upon
a maximum demand of NO.sub.x reduction in an application. As a
result, when the gas turbine engine 12 is not operating at full or
base load and the gas turbine engine 12 is not producing maximum
NO.sub.x levels or a maximum flow of exhaust gas 26, the SCR system
30 may have additional (e.g., unused) capacity for NO.sub.x
reduction. In the manner described below, at less than full gas
turbine engine 12 loads, the additional or unused NO.sub.x
reduction capacity of the SCR system 30 may be utilized to improve
combustor 24 operation and life by reducing the usage of other
emissions control measures in the combustors. Additionally, in
certain embodiments, the SCR system 30 may be over-designed to
provide additional NO.sub.x reduction capacity. As such, the gas
turbine engine 12 may be operated at a full load, and the unused
capacity of the SCR system 30 may be utilized to further reduce
NO.sub.x levels in the exhaust gas stream 26.
[0022] As mentioned above, one technique for removing or reducing
the amount of NO.sub.x in an exhaust gas stream is by using a
Selective Catalytic Reduction (SCR) process. For example, in an SCR
process for removing NO.sub.x from the exhaust gas stream 26,
ammonia (NH.sub.3) is injected into the exhaust gas stream (e.g.,
exhaust gas 26) and reacts with the NO.sub.x to produce nitrogen
(N.sub.2) and water (H.sub.2O). As will be appreciated, the
effectiveness of this SCR process may be at least partially
dependent on the amount of ammonia (NH.sub.3) injected into the
exhaust gas 26. As discussed in detail below, the amount of ammonia
(NH.sub.3) injected into the exhaust gas 26 may be regulated along
with other operating parameters of the gas turbine engine 12 to
maintain emissions levels (e.g., NO.sub.x emissions levels) below
one or more threshold levels in the gas turbine engine 12 (e.g.,
exhaust gas 26) and the overall turbine system (e.g., stack
emissions).
[0023] As shown in FIG. 1, the SCR system 30 includes a reductant
(e.g., ammonia (NH.sub.3)) injection grid 32 configured to inject
the reductant into the stream of exhaust gas 26, as indicated by
arrows 34. In one embodiment, the reductant injection grid 32 may
include a network of pipes with openings for injecting reductant
into the stream of exhaust gas 26. Reductant injection (e.g.,
arrows 34) occurs upstream of an SCR catalyst 37. As will be
appreciated, the reductant and NO.sub.x in the exhaust gas 26 react
as they pass through the SCR catalyst 37 to produce nitrogen
(N.sub.2) and water (H.sub.2O), thus removing NO.sub.x from the
exhaust gas 26. The resulting emissions (e.g., processed exhaust
gas stream 36 or stack emissions) are released into the atmosphere
through a stack 38 of the turbine system 10, as indicated by arrows
40. Furthermore, the stack 36, in some embodiments, may include a
silencer or muffler.
[0024] As shown, the reductant (e.g., ammonia (NH.sub.3)) may be
supplied to the reductant injection grid 32 by a reductant source
42 (e.g., reductant storage tank). Additionally, a valve 44 may
control a flow rate of the reductant supplied to the reductant
injection grid 32. As discussed in detail below, the flow rate of
the reductant may be controlled to achieve a desired NO.sub.x
concentration (e.g., below a threshold level) in the processed
exhaust gas stream 36 (e.g., stack emissions). For example, in
certain embodiments, the flow rate of the reductant may be based at
least partially on the amount of NO.sub.x in the exhaust gas 26
entering the SCR system 30. Additionally, the flow rate of the
reductant may be based at least partially on available NO.sub.x
reduction capacity of the SCR system 30.
[0025] While the present embodiment is generally focused on the
processing and removal of NO.sub.x from the exhaust gas stream 26,
other embodiments may provide for the removal of other combustion
byproducts, such as carbon monoxide or unburned hydrocarbons. As
such, the supplied catalyst may vary depending on the composition
that is being removed from the exhaust gas stream 26. Additionally,
it should be understood that the embodiments disclosed herein are
not limited to the use of one SCR system 30, but may also included
multiple SCR systems 30.
[0026] Still referring to FIG. 1, the turbine system 10 further
includes a turbine system control system 46 configured to regulate
operation of the gas turbine engine 12 and the exhaust processing
system 14. Specifically, the turbine system control system 46
includes an exhaust processing control system 48 and a gas turbine
engine control system 50, which may work together to coordinate
processing and removal of emissions (e.g., NO.sub.x, CO, etc.) from
the exhaust gas stream 26. For example, in the manner described in
detail below, the turbine system control system 46 (e.g., the
exhaust processing control system 48 and/or the gas turbine engine
control system 50) may regulate one or more operating parameters of
the gas turbine engine 12 and/or the SCR system 30 to control the
relative amounts of NO.sub.x reduction in both the exhaust gas 26
and the processed exhaust gas 36. In other words, NO.sub.x
reduction in the SCR system 30 may be increased to enable a
reduction in NO.sub.x emissions control in the gas turbine engine
12.
[0027] As shown, the exhaust processing control system 48 includes
a controller 52 having a microprocessor 54 and a memory 56. For
example, the memory 56 may include any suitable tangible,
computer-readable medium having executable instructions. The
exhaust processing control system 48 further includes an optimizer
58, which may be configured to control or regulate one or more
operating parameters of the turbine system 10 to coordinate (e.g.,
optimize relative amounts of) NO.sub.x reduction in the gas turbine
engine 12 and the SCR system 30. For example, the optimizer 58 may
also include memory 56 with executable instructions for controlling
NO.sub.x reduction in the exhaust gas 26 and processed exhaust gas
36. The exhaust processing control system 48 may regulate one or
more components of the SCR system 30. For example, as shown in the
illustrated embodiment, the exhaust processing control system 48
may regulate operation of the valve 44. In this manner, the exhaust
processing control system 48 may control a flow rate of reductant
(e.g., ammonia (NH.sub.3)) into the SCR system 30, thereby
adjusting the amount of NO.sub.x removal from the exhaust gas 26
downstream from the gas turbine engine 12. The exhaust processing
system 48 may also regulate operation of other components of the
SCR system 30.
[0028] Additionally, exhaust processing control system 48 may
regulate operation of various components of the SCR system 30 based
on measured feedback. For example, the SCR system 30 may include a
sensor 60 configured to measure a reductant "slip" in the SCR
system 30. As mentioned above, when reductant is over-injected into
the exhaust gas 26, an amount of reductant may "slip" or pass
through the SCR system 30 unreacted. As such, the sensor 60 may be
configured to measure an amount of unreacted reductant in the SCR
system 30 and downstream of the reductant injection grid 32.
Furthermore, the SCR system 30 may include a sensor 62 that
continuously monitors the composition of the processed exhaust
stream 36 exiting the stack 38, a sensor 64 configured to measure a
flow rate of reductant supplied to the reductant injection grid 32
from the reductant source 42, and a sensor 66 configured to measure
NO.sub.x in the exhaust gas 26. For example, in certain
embodiments, the controller 52 and the sensors 62 and 66 may
measure emissions parameters using the laser emissions measurement
and control system described in U.S. Pat. No. 8,151,571, which is
hereby incorporated by reference in its entirety. Additionally, in
certain embodiments, the sensor 60 and the controller 52 may
measure reductant slip using the reductant slip control algorithm
described in U.S. Patent Application Publication No.
US2011/0192147, which is hereby incorporated by reference in its
entirety. In the manner described below, the exhaust processing
control system 48 may utilize measured feedback from one or more of
the sensors 60, 62, 64, and 66 or other sensors of the SCR system
30 to regulate and coordinate (e.g., optimize relative amounts of)
NO.sub.x reduction in the exhaust gas 26 and the processed exhaust
gas 36.
[0029] Similarly, the optimizer 58 may further regulate operation
of the gas turbine engine 12. In certain embodiments, the optimizer
58 may regulate operation of one or more components of the gas
turbine engine 12 based on measured feedback from the sensors 60,
62, 64, and 66. For example, a gas turbine controller 68 of the gas
turbine engine control system 40 may receive operation instructions
or feedback from the optimizer 58 and/or the exhaust processing
control system 48. In response, the gas turbine controller 68 may
regulate one or more systems 70 of the gas turbine engine 12. For
example, the gas turbine controller 68 may control operation of a
fuel system 72, which supplies fuel to the combustor 20.
Specifically, the gas turbine controller 68 may control the fuel
system 72 to regulate fuel flow rates, fuel splits (e.g., split of
fuel between 2 or more fuel nozzles and/or combustors), fuel
composition, air-fuel ratios (e.g., fuel-rich, fuel-lean, or
substantially stoichiometric), or other operating parameters
associated with fuel provided to the combustor 20. Additionally,
the gas turbine controller 68 may regulate operation of a water
system 74 of the gas turbine engine 12. As mentioned above, water
or steam may be injected (e.g., from the water system 74) into the
combustor 20 to reduce NO.sub.x in the stream of exhaust gas 26
exiting the turbine 22. However, water (e.g., liquid water or
steam) injected into the combustor 20 may increase pressure
oscillations and vibrations (e.g., combustion dynamics) in the
combustor 20. As a result, in the manner described below, the
turbine system control system 46 (e.g., the exhaust processing
control system 48 and/or the gas turbine engine control system 50)
may be configured to control the amount of water injected into the
combustor 20 from the water system 74 in conjunction with
controlling other operating parameters of the turbine system 10.
Furthermore, the gas turbine controller 68 may regulate or control
other operation systems 76 of the gas turbine engine 12 (e.g.,
based on instructions and/or feedback received from the exhaust
processing control system 48 and/or optimizer 58). For example, the
other operation systems 76 may include a system configured to
regulate a mode of the gas turbine engine 12, a flame temperature
of the combustor 20, and so forth.
[0030] Moreover, the turbine system control system 46 (e.g., the
exhaust processing control system 48 and/or the gas turbine engine
control system 50) may be configured to receive user input 78 and
control operation of the turbine system 10 and NO.sub.x levels
based on the user input 78. For example, the user input 78 may
include reductant price, an exhaust gas NO.sub.x set point,
electricity price, electricity demand, fuel price, combustor outage
intervals, NO.sub.x credits, other financial information, and/or
other information related to operation of the turbine system 10.
Such user input 78 information may further be incorporated into
control of NO.sub.x reduction in the exhaust gas 26 (e.g., NO.sub.x
control within the gas turbine engine 12) and the processed exhaust
gas 36 (e.g., NO.sub.x control within the exhaust processing system
14). In certain embodiments, further constraints or control
parameters may be used by the optimizer 58. For example, additional
constraints may include allowable reductant slip based on
environmental regulations, stack 38 CO emission regulations, or
other operational constraints.
[0031] As mentioned above, the optimizer 58 is configured to
regulate operation of the turbine system 10 to control NO.sub.x
reduction within the turbine system 10, while increasing hardware
and part life of the turbine system 10 (e.g., by reducing
combustion dynamics, reducing CO, increasing lean blow out margins,
etc.). For example, in one embodiment, variations in NO.sub.x
levels in the exhaust gas 26 may be scheduled (e.g., preset), and
the SCR system 30 may be controlled to achieve permitted NO.sub.x
levels in the processed exhaust gas 36 released through the stack
38. In another embodiment, reductant slip (e.g., unreacted
reductant) and NO.sub.x levels in the processed exhaust gas 36 may
be simultaneously controlled to achieve a permitted level of
NO.sub.x in the processed exhaust gas 36. In such an embodiment,
one or more operating conditions of the gas turbine engine 12 may
be controlled to reduce NO.sub.x control measures within the gas
turbine engine 12 causing an increase in the amount of NO.sub.x in
the exhaust gas 26 entering the SCR system 30, thereby utilizing
the capacity of the SCR system 30 to reduce NO.sub.x levels in the
exhaust gas 26 to permitted levels. In this manner, water/steam
injection and/or other NO.sub.x reduction measures of the gas
turbine engine 12 may be reduced, thereby reducing combustion
dynamics and extending combustor 20 life, increasing lean blow out
margin and reducing combustor trips and flame out, reducing load
turndown, and so forth.
[0032] FIG. 2 is a flow chart illustrating a method 100 for
controlling emissions of the turbine system 10 using the turbine
system control system 46. As indicated by step 102, variations in
gas turbine engine 12 NO.sub.x levels (e.g., levels of NO.sub.x in
exhaust gas 26 exiting the gas turbine engine 12) may be scheduled.
For example, NO.sub.x levels in the exhaust gas 26 exiting the gas
turbine engine 12 may vary based on scheduled loads, operating
modes (e.g., start up, steady state, shut down, part load, turn
down, etc.), or operating times of the gas turbine engine 12. In
one embodiment, a first level of NO.sub.x emissions may be
permitted or output of the gas turbine engine 12 for a first period
of a time, and, subsequently, a second level of NO.sub.x emissions
may be permitted or output from the gas turbine engine 12 for a
second period of time. During the first and second periods of time,
the SCR system 30 may be controlled to further reduce NO.sub.x
emissions in the exhaust gas 26 to a permitted level of the
processed exhaust gas 36. In certain embodiments, the NO.sub.x
levels in the exhaust gas 26 exiting the gas turbine engine 12 and
entering the SCR system 30 may be scheduled or preset in the
turbine system control system 46 as user input 78. As will be
appreciated, the gas turbine engine controls system 50 may be
configured to control one or more operating systems 70 (e.g., fuel
system 72, water system 74, or other system 76) to achieve the
scheduled or preset NO.sub.x levels in the exhaust gas 26. In
certain embodiments, the sensor 66 may measure NO.sub.x levels in
the exhaust gas 26 exiting the gas turbine engine 12, and the
turbine system control system 48 may communicate the feedback or
instructions to the gas turbine controller 68 to regulate one or
more of the operating systems 70 to achieve the scheduled NO.sub.x
levels.
[0033] With the NO.sub.x levels of the exhaust gas 26 exiting the
gas turbine engine 12 scheduled or preset, the SCR system 30 may be
operated or controlled (e.g., by the exhaust processing control
system 48) to achieve permitted levels of NO.sub.x in the processed
exhaust gas 36 exiting the stack 38, as indicated by step 104. For
example, based on the NO.sub.x levels in the exhaust gas 26
entering the SCR system 30, the exhaust processing control system
48 may regulate operation of the valve 44 to control an amount of
reductant (e.g., ammonia) entering the SCR system 30 through the
reductant injection grid 32. Specifically, the amount of reductant
injected into the SCR system 30 may be controlled to achieve a
permitted NO.sub.x level of the processed exhaust gas 36. For
example, the exhaust processing control system 48 may receive a
measured amount of NO.sub.x in the processed exhaust gas 36 from
the sensor 62, and the controller 52 may regulate operation of the
valve 44 to inject a sufficient amount of reductant into the SCR
system 30 to reduce NO.sub.x levels in the processed exhaust gas 36
to a permitted level.
[0034] FIG. 3 is a flow chart illustrating a method 120 for
controlling emissions of the turbine system 10 using the turbine
system control system 46. For example, the illustrated method 120
may be used for increasing (e.g., maximizing) the amount of
NO.sub.x in the exhaust gases 26 exiting the gas turbine engine 12
and entering the SCR system 30, while achieving permitted NO.sub.x
levels in the processed exhaust gases 36 exiting the turbine system
10 through the stack 38. First, as indicated by step 122, a desired
or target value for NO.sub.x in the exhaust gas 26 exiting the gas
turbine engine 12 and entering the SCR system 30 may be set. For
example, the desired or target value for NO.sub.x levels in the
exhaust gas 26 exiting the gas turbine engine 12 and entering the
SCR system 30 may be set in the optimizer 58 through user input 78.
Thereafter, a desired or target value for reductant slip in the SCR
system 30 may be set, as indicated by step 124. For example, the
desired or target value for reductant slip in the SCR system 30 may
be set in the optimizer 58 through user input 78. In certain
embodiments, the desired or target value for reductant slip in the
SCR system 30 may be based on an allowable or permitted amount
based on certain regulations (e.g., environmental regulations).
Next, a desired or target value for NO.sub.x levels in the
processed exhaust gas 36 exiting the stack 38 of the exhaust
processing system 14 may be set, as indicated in step 126. As
similarly described above, the desired or target value for NO.sub.x
in the processed exhaust gas 36 may be set in the optimizer 58
through user input 78. Additionally, the desired or target value
for NO.sub.x in the processed exhaust gas 36 may be based on an
allowable or permitted amount based on certain regulations (e.g.,
environmental regulations).
[0035] Once the above mentioned values are set (e.g., by user input
78, preprogrammed, or otherwise), reductant may be injected into
the SCR system 30 to achieve the desired reductant slip value, as
indicated by step 128. For example, the controller 52 of the
exhaust processing control system 48 may regulate operation of the
valve 44 to control flow of reductant from the reductant source 42
to the reductant injection grid 32 of the SCR system 30.
Additionally, the exhaust processing control system 48 may receive
a feedback of measured reductant slip (e.g., unreacted reductant)
from the sensor 60. Using the measured feedback from the sensor 60,
the controller 52 may further regulate the flow of reductant into
the SCR system 30 (e.g., by controlling operation of the valve 44)
to achieve the desired value for reductant slip. Furthermore, in
certain embodiments, reductant slip may be controlled using one or
more algorithms, which may be stored in the memory 56 of the
exhaust processing control system 48. For example, in one
embodiment, the algorithm may be the reductant slip control
algorithm described in U.S. Patent Application Publication No.
US2011/0192147, which is hereby incorporated by reference in its
entirety.
[0036] Thereafter, an adjustment for the desired value of NO.sub.x
in the exhaust gas 26 entering the SCR system 30 may be determined,
as indicated by step 130. For example, based at least partially on
measured feedback received by the sensors 60 and/or 62, the desired
value of NO.sub.x in the exhaust gas 26 exiting the gas turbine
engine 12 and entering the SCR system 30 may increase or decrease.
Accordingly, the optimizer 58 may calculate an appropriate
adjustment. For example, if the optimizer 58 calculates that the
SCR system 30 has additional unused capacity (e.g., based on a
measured reductant slip determined by the sensor 60), then the
optimizer 58 may determine that the desired value of NO.sub.x in
the exhaust gas 26 entering the SCR system 30 should increase.
[0037] After the adjustment for the desired value of NO.sub.x in
the exhaust gas 26 entering the SCR system 30 is determined, the
turbine system control system 46 (e.g., optimizer 58) may determine
an adjustment of at least one gas turbine engine 12 operating
parameter to achieve the new desired value for NO.sub.x in the
exhaust gas 26 entering the SCR system 30, as indicated by step
132. For example, if the optimizer 58 determines that the desired
value for NO.sub.x in the exhaust gas 26 entering the SCR system 30
should increase, the gas turbine controller 68 may operate the
water system 74 of the gas turbine engine 12 to decrease
water/steam injection into the combustor 20. As a result,
combustion dynamics in the combustor 20 may be reduced due to the
reduced water/steam injection, thereby reducing wear on combustor
20 components and increasing the useful life of the combustor 20.
Other gas turbine engine 12 operating parameters that may be
altered by the gas turbine controller 68 based on the adjustment
determined by the optimizer 58 may include adjustments to fuel
splits (e.g., adjusting one or more fuel flows to one or more fuel
nozzles and/or combustors), flame temperature, fuel/air ratio (or
equivalence ratio), fuel composition, and so forth.
[0038] After the adjustment is made to one or more operating
parameters of the gas turbine engine 12 to achieve the new desired
value for NO.sub.x in the exhaust gas 26 entering the SCR system
30, the turbine system control system 46 (e.g., the optimizer 58)
may again sequentially perform steps 128, 130, and 132 in a loop
(e.g., a continuous loop). That is, reductant may be injected into
the SCR system 30 to achieve the desired reductant slip value
measured by sensor 30, an adjustment for the desired value for
NO.sub.x in the exhaust gas 26 entering the SCR system 30 may be
determined, and one or more operating parameter adjustments may be
determined and implemented for the gas turbine engine 12. In this
manner, the operation of the gas turbine engine 12 and the SCR
system 30 may be coordinated (e.g., simultaneously coordinated and
controlled) to utilize available capacity of the SCR system 30
during less than full or base loads of the gas turbine engine 12,
reduce combustion dynamics in the combustor 20, reduce CO emissions
(e.g., by increasing NO.sub.x emissions in the gas turbine engine
12 upstream of the SCR system 30, increase lean blow out margin,
reduce turndown load, and so forth.
[0039] As discussed in detail above, the turbine system 10, which
may be a simple cycle heavy-duty gas turbine system or an aircraft
engine derivative combustion system, includes the turbine system
control system 46 configured to regulate and coordinate operation
of the gas turbine engine 12 and the SCR system 30 to achieve a
desired quality of emissions (e.g., stack emissions) produced by
the turbine system 10. For instance, the control system 46 may be
configured to utilize available NO.sub.x reduction capacity of the
SCR system 30 to reduce NO.sub.x emission levels, such that other
emissions control measures may be reduced to improve performance,
efficiency, longevity, and/or power output of the gas turbine
engine 12. Specifically, when the gas turbine engine 12 is not
operating at a full or base load and the SCR system 30 has unused
NO.sub.x reduction capacity, operating parameters of the gas
turbine engine 12 may be adjusted to potentially increase NO.sub.x
levels in the exhaust gases 26 produced by the gas turbine engine
12 while reducing mechanical and thermal fatigue to combustor
hardware, increasing lean blow out margins, reducing turndown load,
reducing other emissions compounds (e.g., CO), and so forth. For
example, the variations in NO.sub.x levels in the exhaust gas 26
produced by the gas turbine engine 12 and entering the SCR system
30 may be preset or scheduled. That is, NO.sub.x levels in the
exhaust gas 26 may be produced at a first level for a first period
of time and at a second level for a second period of time, and the
SCR system 30 may further reduce NO.sub.x levels in the processed
exhaust gas 36 accordingly. Additionally, operation of the SCR
system 30 and the gas turbine engine 12 may be simultaneously
controlled and coordinated to utilize available NO.sub.x reduction
capacity of the SCR system 30.
[0040] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal language of the claims.
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