U.S. patent application number 12/554459 was filed with the patent office on 2011-03-10 for system for combustion optimization using quantum cascade lasers.
This patent application is currently assigned to General Electric Company. Invention is credited to David Moyeda, William Randall Seeker, Michelle Simpson, Neil Colin Widmer.
Application Number | 20110056416 12/554459 |
Document ID | / |
Family ID | 43646672 |
Filed Date | 2011-03-10 |
United States Patent
Application |
20110056416 |
Kind Code |
A1 |
Widmer; Neil Colin ; et
al. |
March 10, 2011 |
SYSTEM FOR COMBUSTION OPTIMIZATION USING QUANTUM CASCADE LASERS
Abstract
A system with a boiler and a turbine, and an associated control
method. The method includes sensing a plurality of operating
conditions at a first common boiler location. At least one of the
plurality of operating conditions sensed at the first common
location is indicative of a combustion anomaly occurring during
operation. The combustion anomaly indicated by the plurality of
operating conditions at the first common location is traced back to
an offending burner that is at least partially responsible for the
combustion anomaly based on a model that takes into consideration
at least two of the plurality of operating conditions sensed at the
first common location. At least one of a process input and a boiler
configuration is adjusted to establish a desired value of the
operating conditions at the first common location.
Inventors: |
Widmer; Neil Colin; (San
Clemente, CA) ; Moyeda; David; (Santa Ana, CA)
; Seeker; William Randall; (San Clemente, CA) ;
Simpson; Michelle; (Simpsonville, SC) |
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
43646672 |
Appl. No.: |
12/554459 |
Filed: |
September 4, 2009 |
Current U.S.
Class: |
110/185 ;
110/188; 110/190; 110/234; 431/4; 431/76; 431/79; 60/664 |
Current CPC
Class: |
F23N 5/242 20130101;
F23N 1/022 20130101; F23N 5/022 20130101; F22B 37/38 20130101; F23N
2237/02 20200101; F23N 5/082 20130101; F23N 5/003 20130101; F22B
35/00 20130101; F23J 7/00 20130101 |
Class at
Publication: |
110/185 ;
110/188; 110/190; 431/76; 431/79; 431/4; 110/234; 60/664 |
International
Class: |
F23N 5/00 20060101
F23N005/00; F23N 5/08 20060101 F23N005/08; F23N 5/24 20060101
F23N005/24; F23J 7/00 20060101 F23J007/00; F01K 11/02 20060101
F01K011/02 |
Claims
1. A method of controlling operation of a system that includes a
boiler with a plurality of burners, the method including: sensing a
plurality of operating conditions at a first common location along
the boiler, wherein at least one of the plurality of operating
conditions sensed at the first common location is indicative of a
combustion anomaly occurring during operation of the boiler;
tracing the combustion anomaly back to an offending burner that is
at least partially responsible for the combustion anomaly based on
a model that takes into consideration at least two of the plurality
of operating conditions sensed at the first common location; and
adjusting at least one of a process input and a boiler
configuration to establish a desired value of the operating
conditions at the first common location.
2. The method of claim 1, wherein at least one of the operating
conditions at the first common location exceeds an acceptable level
above which a sensor placed at the first common location for
sensing a second of the operating conditions would be damaged, and
wherein sensing of the operating conditions at the first common
location includes non-invasively sensing the operating conditions
with a single sensor that is remotely located from the first common
location.
3. The method of claim 2, wherein the single sensor is selected
from the group consisting of a quantum cascade laser and a tunable
diode laser aimed to project laser light generally toward the first
common location for sensing the plurality of operating conditions
at the first common location.
4. The method of claim 2, wherein the operating conditions to be
sensed at the first common location include a temperature and a
quantity of carbon monoxide, wherein the temperature sensed at the
first common location is greater than a maximum temperature that a
carbon monoxide sensor can withstand.
5. The method of claim 1, wherein adjusting at least one of the
process input and the boiler configuration includes adjusting a
flow rate of a process input being introduced to the offending
burner to establish desired values of the operating conditions at
the first common location.
6. The method of claim 5, wherein the process input includes at
least one of a fuel and combustion air being introduced to the
offending burner.
7. The method of claim 5, wherein the offending burner is
designated as one of the plurality of burners that most
significantly contributes to the combustion anomaly indicated by
the at least one of the operating conditions at the first common
location relative to non-offending burners.
8. The method of claim 1, wherein the plurality of operating
conditions at the first common location includes two or more of
temperature, oxygen level, carbon monoxide level, carbon dioxide
level, NO.sub.x level, SO.sub.x level, and ammonia level, wherein x
is an integer independently selected to be 1, 2 or 3.
9. The method of claim 1, wherein adjusting the at least one of the
process input and the boiler configuration produces an exhaust
including a NO.sub.x emission that is maintained below a specified
level, wherein x is an integer independently selected to be 1 or
2.
10. The method of claim 1, wherein the process input includes a
flow rate of an additive being introduced to the boiler by an
injector.
11. The method of claim 1, wherein the boiler configuration
includes an angle at which an injector introduces a process input
into the boiler.
12. The method of claim 1, wherein the boiler includes a plurality
of process inputs selected from the group consisting of combustion
air, a fuel, a reagent, and an additive, the method further
including designating at least one of the process inputs to be a
significant process input that is present in a greater proportion
at a region within the boiler than the significant process input
would be if the inputs were distributed uniformly throughout the
boiler.
13. The method of claim 2, wherein adjusting at least one of the
process input and the boiler configuration includes varying a flow
rate of the significant process input to establish the desired
value of the operating condition at the first common location.
14. A system including: a steam-driven turbine; a boiler including
a plurality of burners arranged in an array to burn a hydrocarbon
fuel; a plurality of sensors each adapted to sense a plurality of
operating conditions at a common location within the boiler and to
transmit a signal indicative of a combustion anomaly when one or
more of the operating conditions falls outside of a predetermined
range of suitable values indicative of desired combustion; an
actuator for controlling at least one of a process input and a
boiler configuration to affect operation of at least one of the
burners; and a controller in communication with the plurality of
sensors to receive the signals indicative of the combustion
anomaly, wherein, responsive to receiving the signals the
controller traces the one or more operating conditions outside of
the predetermined range of suitable values to identify an offending
burner contributing to the combustion anomaly and controls the
actuator to adjust the at least one of the process input and the
boiler configuration to bring the one or more operating conditions
into the predetermined range of suitable values.
15. The system of claim 4, wherein at least one of the plurality of
sensors is a non-invasive sensor for sensing the plurality of
operating conditions in a non-invasive manner.
16. The system of claim 5, wherein the non-invasive sensor is
selected from a group consisting of a quantum cascade laser, and a
tunable diode laser.
17. The system of claim 4, wherein the operating conditions to be
sensed at the common locations include a temperature and a quantity
of carbon monoxide.
18. A system including: a steam-driven turbine; a boiler including
a plurality of burners arranged in an array to burn a hydrocarbon
fuel; a plurality of non-invasive sensors each adapted to remotely
sense a plurality of operating conditions at a common location
within the boiler and to transmit a signal indicative of a
combustion anomaly when at least one of the operating conditions
falls outside of a predetermined range of suitable values
indicative of desired combustion; a controller in communication
with the plurality of non-invasive sensors to receive the signals
indicative of the combustion anomaly, the controller including a
computer-accessible memory storing a model that relates the
operating conditions falling outside of the predetermined range of
suitable values from one or more of the sensors to at least one
offending burner contributing to the combustion anomaly; and an
actuator to be controlled by the controller for controlling at
least one of a flow rate of the hydrocarbon fuel introduced to the
offending burner, a flow rate of air introduced to the offending
burner, a flow rate of an additive introduced to the boiler through
an injector, and an angle of the injector for introducing the
additive into the boiler to bring the operating conditions into the
predetermined range of suitable values.
19. The system of claim 8, wherein the computer-accessible memory
stores a plurality of models that relate the temperature and the
level of the combustion byproduct sensed by a plurality of
different sensors to the offending burner contributing to the
combustion anomaly.
20. The system of claim 18, wherein the non-invasive sensor is
selected from a group consisting of a quantum cascade laser and a
tunable diode laser.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates generally to a method and apparatus
for controlling operation of a boiler that generates steam to drive
a turbine or provide process steam or heating, and more
specifically to method and apparatus for monitoring and controlling
combustion within a boiler by sensing a plurality of operating
conditions at a common location with a common sensor.
[0003] 2. Description of Related Art
[0004] One method of generating electricity includes driving a
turbine generator with steam. A boiler for generating the steam
commonly includes a furnace with an array of individual burners for
burning the hydrocarbon fuel in the presence of oxygen to raise the
temperature of water and produce the steam to be delivered to the
turbine. The combustion performance of an individual burner
provided to the furnace can affect the combustion performance
locally within the furnace, and thereby affect the overall
performance of the boiler as a whole.
[0005] If one or more of the burners is not operating in an optimal
manner, a condition referred to as a combustion anomaly, the boiler
can emit unsatisfactory levels of by products such as oxides of
nitrogen ("NO.sub.X"), carbon monoxide ("CO"), mercury ("Hg"), and
possibly other byproducts such as unburned carbon (commonly
expressed as loss-on-ignition or "LOI"). The combustion anomaly can
also result in fuel-rich gases and high local gas temperatures that
can contribute to the formation of difficult to remove ash deposits
called slag, or can cause boiler tube-wall wastage through
corrosion and thermal fatigue. In such circumstances the offending
burner(s) must be singled out from the array of burners, and then
adjusted to optimize performance of the boiler. Once the offending
burner(s) is identified, the performance of that burner can be
optimized by means of combustion control, which can include varying
the flow rate at which the hydrocarbon fuel is introduced to the
burner, the flow rate at which air is introduced to the burner, the
rotational velocity component, i.e. spin, of the feed, the angle of
injection, an additive level or other suitable variable that can
rectify the combustion anomaly.
[0006] Traditional boiler control systems have relied upon the
monitoring of the exhaust from the furnace as a whole (i.e., the
collective exhaust resulting from operation of all burners
operating simultaneously) to detect combustion anomalies. In
response to the detection of a combustion anomaly based on a
measured quantity from this collective exhaust the supply of fuel
and/or air to the entire array of burners could be adjusted in an
attempt to optimize operation of the boiler. Such control methods
fail to consider the local effects each burner has on the boiler,
and fails to attribute the individual contribution of each burner
to the combustion anomaly.
[0007] More recently, attempts have been made to trace a combustion
anomaly back to one or more offending burners, from among the
entire array of burners that is/are the primary cause of the
combustion anomaly. Determining the presence of a combustion
anomaly and identifying the offending burner(s), however, is
typically not determined as a function of a single operating
condition, such as a measured temperature, at a particular location
within the boiler. Instead, to identify, or at least narrow down
the location of the offending burner(s), such control methods rely
on a plurality of measured operating conditions sensed at various
different locations within the boiler.
[0008] Arrays of individual sensors are disposed at various
different locations throughout the boiler to monitor different
operating conditions at each of those different locations. For
example, the concentration of carbon monoxide ("CO") has been
monitored by an array of sensors disposed at an exhaust port of the
boiler downstream of the furnace exit. Further, an array of
temperature sensors has been disposed adjacent to a nose of the
furnace provided to the boiler to monitor the temperatures near the
burners. The temperatures near the burners to which the temperature
sensors are exposed are typically too high for the CO concentration
sensors to be co-located with the temperature sensors. Thus, the
array of CO concentration sensors is spatially located away from
the temperature sensors at another, distant location of the boiler
where they are subjected to much lower temperatures that will not
damage the CO concentration sensors. But in order to consider both
the measured CO concentration and the measured temperature at a
common location in the boiler to evaluate a combustion anomaly, one
of these measured operating conditions was required to be mapped to
correspond to an equivalent value at the location of the other
operating condition. In other words, the CO concentration measured
by each CO concentration sensor adjacent the exhaust port, for
example, was adjusted to correspond to the value of the CO
concentration that could be expected to be measured at the location
of each respective temperature sensor. Thus, the measured
temperature and the equivalent CO concentration at a common
location in the boiler could be used to determine whether a
combustion anomaly has occurred, and if so, which of the burners is
contributing to the combustion anomaly.
[0009] Such attempts have improved boiler control over the
traditional methods of controlling the boiler solely on the CO
concentration at the exhaust port. But the mapping of a sensed
operating condition from one location to another location within
the boiler introduces a degree of error in evaluating a combustion
anomaly, limiting the ability to effectively identify the offending
burner(s). Further, the mapping requires the use of many
mathematical models and robust control equipment, making boiler
control expensive and complex.
[0010] Accordingly, there is a need in the art for a method and
apparatus for controlling operation of a boiler to optimize
performance thereof. The method and apparatus can allow for sensing
a plurality of operating conditions at a common location within the
boiler to detect a combustion anomaly and allow for optimization of
boiler operation.
BRIEF DESCRIPTION OF THE INVENTION
[0011] The following summary presents a simplified summary in order
to provide a basic understanding of some aspects of the systems
and/or methods discussed herein. This summary is not an extensive
overview of the systems and/or methods discussed herein. It is not
intended to identify key/critical elements or to delineate the
scope of such systems and/or methods. Its sole purpose is to
present some concepts in a simplified form as a prelude to the more
detailed description that is presented later.
[0012] According to one aspect, the invention provides a method of
controlling operation of a system that includes a boiler with a
plurality of burners. The method includes sensing a plurality of
operating conditions at a first common location along the boiler.
At least one of the plurality of operating conditions sensed at the
first common location is indicative of a combustion anomaly
occurring during operation of the boiler. The method includes
tracing the combustion anomaly back to an offending burner that is
at least partially responsible for the combustion anomaly based on
a model that takes into consideration at least two of the plurality
of operating conditions sensed at the first common location. The
method includes adjusting at least one of a process input and a
boiler configuration to establish a desired value of the operating
conditions at the first common location.
[0013] According to another aspect, the invention provides a system
that includes a steam-driven turbine and a boiler. The boiler
includes a plurality of burners arranged in an array to burn a
hydrocarbon fuel. The system includes a plurality of sensors, each
adapted to sense a plurality of operating conditions at a common
location within the boiler and to transmit a signal indicative of a
combustion anomaly when one or more of the operating conditions
falls outside of a predetermined range of suitable values
indicative of desired combustion. The system includes an actuator
for controlling at least one of a process input and a boiler
configuration to affect operation of at least one of the burners.
The system includes a controller in communication with the
plurality of sensors to receive the signals indicative of the
combustion anomaly, wherein, responsive to receiving the signals
the controller traces the one or more operating conditions outside
of the predetermined range of suitable values to identify an
offending burner contributing to the combustion anomaly and
controls the actuator to adjust the at least one of the process
input and the boiler configuration to bring the one or more
operating conditions into the predetermined range of suitable
values.
[0014] According to yet another aspect, the invention provides a
system including a steam-driven turbine and a boiler. The boiler
includes a plurality of burners arranged in an array to burn a
hydrocarbon fuel. The system includes a plurality of non-invasive
sensors each adapted to remotely sense a plurality of operating
conditions at a common location within the boiler and to transmit a
signal indicative of a combustion anomaly when at least one of the
operating conditions falls outside of a predetermined range of
suitable values indicative of desired combustion. The system
includes a controller in communication with the plurality of
non-invasive sensors to receive the signals indicative of the
combustion anomaly. The controller includes a computer-accessible
memory storing a model that relates the operating conditions
falling outside of the predetermined range of suitable values from
one or more of the sensors to at least one offending burner
contributing to the combustion anomaly. The system includes an
actuator to be controlled by the controller for controlling at
least one of a flow rate of the hydrocarbon fuel introduced to the
offending burner, a flow rate of air introduced to the offending
burner, a flow rate of an additive introduced to the boiler through
an injector, and an angle of the injector for introducing the
additive into the boiler to bring the operating conditions into the
predetermined range of suitable values.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The invention may take physical form in certain parts and
arrangement of parts, embodiments of which will be described in
detail in this specification and illustrated in the accompanying
drawings which form a part hereof and wherein:
[0016] FIG. 1 is a schematic illustration of a power generating
system that includes a coal-fired boiler;
[0017] FIG. 2 is a schematic illustration of a furnace provided to
the boiler shown in FIG. 1, wherein a portion of the furnace is
cutaway;
[0018] FIG. 3 is a flow diagram illustrating an embodiment of a
method for controlling combustion within a coal-fired boiler;
[0019] FIGS. 4A-4D are cross sectional views of an exhaust port of
a boiler divided into zones across which combustion gradients are
to be minimized according to a method of controlling operation of
the boiler; and
[0020] FIG. 5 is a schematic view of a control system for
controlling combustion within a boiler to minimize combustion
gradients.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Example embodiments that incorporate one or more aspects of
the invention are described and illustrated in the drawings. These
illustrated examples are not intended to be a limitation on the
invention. For example, one or more aspects of the invention can be
utilized in other embodiments and even other types of devices.
Moreover, certain terminology is used herein for convenience only
and is not to be taken as a limitation on the invention. Still
further, in the drawings, the same reference numerals are employed
for designating the same elements.
[0022] A method of optimizing operation of a fuel fired boiler is
described below in detail. The method includes the use of a
plurality of different sensors at different spatial locations
within a fuel fired boiler furnace to track in-furnace combustion
conditions and the relative differences between the performance of
individual burners. Each of the sensors can be used to sense a
plurality of operating conditions at the different spatial
locations to make adjustments to individual burners and yield an
optimized boiler performance. The optimized operating burner
conditions can vary from one burner to another. This means that one
or both of the air flow and fuel flow, for example, can vary from
burner to burner and that the air to fuel ratio to individual
burners is not predetermined. Rather, each burner can be
individually biased and adjusted to meet boiler performance
objectives as indicated by the in-furnace sensors as described in
detail below. Optimized performance includes, for example, reduced
NO.sub.x emissions, reduced LOI emissions, increased efficiency,
increased power output, improved superheat temperature profile,
reduced slagging, reduce waterwall wastage, and/or reduced opacity
relative to un-optimized operation of the boiler. Corrective
actions such as burner adjustments, boiler configuration
adjustments, or both can include, for example, fuel flow, air flow,
fuel to air ratio, burner register settings, overfire airflows, the
orientation of injectors 55 for introducing an additive (including
air or fuel) into the furnace, and other furnace input
settings.
[0023] Referring to the drawings, FIG. 1 is a schematic view of a
power generating system 10 that includes, in an exemplary
embodiment, a boiler 12 coupled to a steam-turbine generator 14.
Steam is produced in the boiler 12 and subsequently flows through a
steam pipe 16 to the generator 14, which is driven by the steam to
produce electric power. The boiler 12 burns a fossil fuel such as
coal, or other suitable hydrocarbon fuel source, for example, in a
furnace 18 to produce the heat required to convert water into steam
for driving the generator 14. Of course, in other embodiments the
fossil fuel burned in the furnace 18 can include oil, natural gas
or any other suitably combustible material. However, for the sake
of brevity the description that follows will refer to coal as the
fuel. Crushed coal, for example, is stored in a silo 20 and is
ground or pulverized into fine particulates by a pulverizer or mill
22. A coal feeder 24 adjusts the flow of coal from the coal silo 20
into the mill 22. A forced air source such as a fan 26, for
example, is used to create an airflow including entrained
particulate coal from the mill 22 to convey the coal particles to
furnace 18 where the coal is burned by burners 28. The air from the
fan 26 used to convey the coal particles from the mill 22 to the
burners 28 is referred to as primary air.
[0024] A second fan 30 supplies secondary air to the burners 28
through an air conduit 32 and a windbox 33. The secondary air is
heated before being introduced into the furnace 18 upon passing
through a regenerative heat exchanger 34, transferring heat from a
boiler exhaust line 36 to the air conduit 32. Secondary air can
optionally be introduced into the furnace 18 in addition to the
primary air when there is insufficient oxygen present within the
furnace 18 to allow complete combustion of the fuel being burned, a
condition referred to herein as an oxygen deficiency.
[0025] The boiler 12 also includes a network of actuators that are
operable to control at least one of a process input and a boiler
configuration to affect the combustion occurring within the furnace
18. The actuators can be adjusted to regulate the process inputs
such as a flow rate of fuel and/or air into the furnace 18 to bring
the operating conditions sensed by an array of sensors 38 (FIG. 2)
provided to the furnace 18 within a predetermined range of suitable
values indicative of substantially-balanced combustion as described
below. For instance, valves 41 (FIG. 1) between the fan 26 and the
furnace 18 can be adjusted to regulate the supply of fuel to the
burners 28, individually and/or collectively. Similarly, a damper
52 can be adjusted to regulate the flow of primary air, secondary
air, or both primary and secondary air into the furnace 18.
Operation of the fans 26, 30, coal feeder 24, and mill 22, alone or
in any combination, can optionally be adjusted and controlled to
act as the actuators and bring the operating conditions into the
predetermined range of suitable values.
[0026] According to alternate embodiments, the configuration of the
boiler 12 itself can be adjusted instead of, or in addition to the
actuators in an attempt to bring the values of the operating
conditions to within the predetermined range of suitable values.
For example, the furnace 18 can optionally be provided with an
additive injector 55 that penetrates a wall of the furnace 18,
thereby extending into the furnace 18 for injecting a desired
additive from a reservoir 57 into the furnace 18, and optionally
into the primary combustion zone. A myriad of additives (such as a
combustion additive, or magnesium oxide for slag) could be used,
and any specifics about additives should not be considered to be a
limitation upon the invention. The additive can be injected into
the furnace 18. The angle at which the additive injector 55
introduces the additive into the furnace 18 can be adjusted to
affect the operating conditions within the furnace 18.
[0027] The process input(s) associated with each individual burner
28 can optionally be adjusted independent of the process input(s)
of other burners 28 to affect the combustion performance of the
individual burners 28. Likewise, the boiler configuration, such as
the injection angle of a first additive injector 55 can be adjusted
independently of another additive injector (not shown). This
independent adjustment of the boiler configuration can primarily
affect the combustion performance of a burner 28 adjacent to the
first additive injector 55 without significantly affecting the
combustion performance of another burner 28 spatially separated
from the first additive injector 55. Thus, the combustion
performance of each of the burners 28 can be adjusted and corrected
individually to promote substantially-balanced combustion.
[0028] A flue gas including gaseous combustion products such as
fully combusted fuel in the form of CO.sub.2, in addition to
undesirable byproducts such as NO.sub.x, and CO compositions, for
example, travels in a substantially vertical direction upward
within the furnace 18. The flue gas travels upward beyond a nose 35
that protrudes into an interior chamber defined by the furnace 18,
and then generally vertically downward through an exhaust port 37
leading to the exhaust line 36. The exhaust port 37 is said to be
"downstream" of the burners 28 as the flue gas travels from a
region adjacent to the burners 28 and then to the exhaust port 37
in a direction generally indicated by arrow 39 shown in FIG. 2.
Similarly, the burners 28 are said to be "upstream" along the flue
gas path indicated by the arrow 39 relative to the exhaust port
37.
[0029] Substantially-balanced combustion is achieved when a flue
gas has substantially-uniform operating conditions across the
cross-section of the exhaust port 37 of the furnace 18 as described
below with reference to FIGS. 4A-4D. The operating conditions can
be any property within the furnace 18 indicative of the
completeness of combustion of the hydrocarbon fuel attributable to
one or more burners 28 within the furnace 18. Examples of such
operating conditions according to one embodiment can include a
temperature of the flue gas. According to other embodiments, the
operating condition can include a component composition of the flue
gas, wherein the component can be one or more of CO.sub.X (where
X=1 or 2), NO.sub.X (representing any binary compound of oxygen and
nitrogen, or to a mixture of such compounds, such as when X=1 or
2), O.sub.2, N.sub.2, total hydrocarbons ("THC"), volatile organic
compounds ("VOC"), SO.sub.2, SO.sub.3, H.sub.2O, OH radicals, LOI,
and any particulate matter, for example.
[0030] Referring also to FIG. 2, the furnace 18 includes a
plurality of non-invasive sensors 38 arranged a regular, grid
formation and located downstream from a flame envelope 42 formed by
burning coal in burners 28 in a primary combustion zone within the
furnace 18. The grid locations of the sensors 38 can optionally
correspond to the locations of the burners 28, which can also be
arranged in a regular, grid arrangement. For example, one of the
sensors 38 can be substantially vertically aligned in a column 48
with one of the burners 28. The furnace 18 can also include a
plurality of overfire air jets 47 and a plurality of reburn fuel
jets 49 disposed downstream from the burners 28. The reburn fuel
jets 49 introduce fuel into a secondary combustion zone 44
downstream from the primary combustion zone. The fuel from the
reburn fuel jets 49 is mixed with combustion products from the
primary combustion zone in the presence of oxygen from air
introduced into the furnace 18 downstream from the reburn fuel jets
49 by the overfire air jets 47. The combination of the fuel from
the reburn fuel jets 49, the oxygen from the overfire air and the
combustion gasses from the primary combustion zone within the
furnace establishes a balanced stoichiometry that encourages
complete combustion of the fuel and minimizes the formation and
emission of unwanted combustion byproducts such as CO and NO.sub.X,
for example.
[0031] Each sensor 38 can optionally be any non-invasive sensor
capable of sensing a plurality of operating conditions at a common
location within the furnace 18 without physically protruding into
the interior of the furnace, and without physically contacting or
consuming combustion products to sense the operating conditions.
Thus, the non-invasive embodiment of the sensor can measure the
plurality of operating conditions at the common location within the
furnace from a remote spatial location. Each sensor 38 can sense a
qualitative or quantitative value of two or more operating
conditions at substantially the same location within the furnace
18, which can optionally be a location where the sensor would be
damaged when exposed to the operating conditions if physically
located at that location. For example, if the operating conditions
to be sensed at the common location include a temperature and a
quantity of carbon monoxide, the temperature sensed at the common
location is greater than a maximum temperature that a carbon
monoxide sensor can withstand.
[0032] The sensors 38 can also transmit signals indicative of a
combustion anomaly when one or more of the sensed operating
conditions falls outside of a predetermined range of suitable
values indicative of a desired, balanced combustion of the fuel-air
mixture. The sensed value of the operating condition can be
obtained from absolute measurement, relative measurement, and
drawing from analysis of fluctuations in combustion quality.
Examples of suitable non-invasive sensors 38 for sensing the
operating conditions include, but are not limited to, a quantum
cascade laser ("QCL") paired with an optical detector 45 for
receiving laser light 51 from the QCL, tunable diode laser or other
optical sensor, a radiation sensor, and any other sensor that can
measure operating conditions at a common location remotely located
from the sensor itself.
[0033] Although the sensors 38 are described in detail below as
including a combination of QCL and optical detector 45, other
embodiments can include any suitable sensor that can withstand the
conditions at the common location where the plurality of operating
conditions is to be sensed. Further, two sensors could optionally
be co-located according to alternate embodiments to sense their
respective operating condition at the common location. Examples of
such alternate embodiments of sensors 38 include, but are not
limited to LOI sensors, temperature sensors, CO sensors, CO.sub.2
sensors, NO.sub.x sensors, O.sub.2 sensors, THC sensors, volatile
organic compounds ("VOC") sensors, sulfur dioxide (SO.sub.2)
sensors, heat flux sensors, radiance sensors, opacity sensors,
emissivity sensors, moisture sensors, hydroxyl radicals (OH)
sensors, sulfur trioxide (SO.sub.3) sensors, particulate matter
sensors, and emission spectrum sensors.
[0034] FIG. 5 shows an illustrative embodiment of a control system
82 in communication with the plurality of sensors 38 (FIG. 2) to
receive the signals indicative of the combustion anomaly to control
the actuators and execute the control method disclosed herein. As
shown, the control system 82 includes a central processor 84 in
communication with a computer-accessible memory 86. A data bus 88
establishes a communication channel to facilitate the transmission
of signals as part of the method disclosed herein. The
computer-accessible memory 86 stores computer-executable
instructions that, when executed by the central processor 84
instruct the central processor 84 to respond to signals from the
sensors 38 to initiate control of the actuators as needed to
promote substantially-balanced combustion within the furnace 18.
More specifically, responsive to receiving the signals the control
system 82 traces one or more operating conditions sensed by the
sensors 38 that fall outside of the predetermined range of suitable
values to identify an offending burner contributing to a combustion
anomaly. The central processor 84, executing the
computer-executable instructions from the computer-accessible
memory 86 controls one or more of the actuators to adjust the at
least one of the process input and the boiler configuration to
bring the operating conditions into the predetermined range of
suitable values as described in detail below.
[0035] A method of controlling operation of the system 10 specific
to the boiler 12, which includes a plurality of burners 28, in
accordance with an embodiment can be understood with reference to
FIG. 3. The method illustrated in FIG. 3 will be described with
reference to a boiler 12 including a plurality of QCL embodiments
of the sensors 38, each for non-invasively measuring a plurality of
operating conditions along the laser light between the QCL and its
respective optical detector 45. According to such an embodiment,
the method includes sensing a plurality of operating conditions at
a first common location, such as along the laser light 51 (FIG. 2)
for example, within the furnace 18 at 100 (FIG. 3). The first
common location where the plurality of operating conditions are
sensed in the present embodiment can be thought of as an
intersection of the laser light 51 (FIG. 2) and a plane normal to
the path of the laser light 51 within the furnace 18. The sensed
operating conditions at this intersection can represent an average
value of the operating conditions sensed by the QCL embodiment of
the sensors 38 between each QCL and their respective optical
detector 45. For the present embodiment, the plurality of operating
conditions sensed include both the temperature of the flue gas and
an amount of CO in the flue gas at the first common location.
[0036] The value of the operating conditions as determined by the
QCL and its respective optical detector 45 can be recorded in a
computer-accessible memory at 105. Recording the value of the
operating conditions preserves the sensed value of the operating
conditions for comparison with those sensed values during a
subsequent iteration of the present method to determine whether the
combustion anomaly has been improved.
[0037] At least one of the plurality of operating conditions (both
operating conditions in the present example) sensed at the first
common location can be compared at step 107 to a range of
predetermined acceptable values for those operating conditions. If
the sensed value of each operating conditions falls within the
respective predetermined ranges of acceptable values, the boiler 12
is operating properly and substantially-balanced combustion is
achieved. Combustion is maintained at step 109 and the method
returns to step 100 to continue monitoring of the operating
conditions at the first common location.
[0038] If, however, it is determined at step 107 that one or more
of the operating conditions falls outside the predetermined range
of acceptable values for that operating condition, such a condition
is indicative of a combustion anomaly occurring during operation of
the boiler 12. During the combustion anomaly the flue gas exiting
the exhaust port 37 of the furnace 18 of the boiler 12 does not
exhibit substantially-balanced combustion.
[0039] At step 110 in FIG. 3, the combustion anomaly indicated by
one or more of the plurality of operating conditions sensed at the
first common location is traced back to an offending burner that is
at least partially responsible for the combustion anomaly. Tracing
the combustion anomaly is based on a mathematical model that takes
into consideration at least two of the plurality of operating
conditions sensed at the first common location. Since the plurality
of operating conditions are sensed at approximately the same
location within the furnace 18, these sensed operating conditions
can be traced back to the offending burner without mapping one of
the sensed operating conditions from a different spatial location
within the furnace 18 to another, different spatial location where
another operating condition was sensed. In other words, both the
temperature and amount of CO sensed in the present example at the
first common location within the furnace 18 can be traced from that
same first common location back to one or more offending burners.
Both are sensed at the first common location within the furnace 18,
and thus, one does not first have to be mapped to an equivalent
value at another location where the other operating condition is
sensed as a precursor to tracing the operating conditions back to
the offending burner. Instead, each of the operating conditions can
be considered as sensed at the first common location in identifying
one or more offending burners responsible for the combustion
anomaly indicated by one or both of the operating conditions
falling outside of a predetermined range of acceptable values for
those operating conditions.
[0040] The value of each of the sensed operating conditions can
optionally be used in tracking the combustion anomaly back to the
offending burner(s) 28, and can optionally be used to identify the
one or more burners 28 providing the most significant contributions
to the combustion anomaly. For instance, a burner 28 vertically
aligned with a QCL embodiment of a sensor 38 and a respective
optical detector 45 may contribute more significantly to an
under-temperature condition at the common location where the
temperature is measured than another burner 28 horizontally offset
from the QCL and respectively optical detector 45. Further, if an
amount of CO detected by the sensor 38 at the first common location
where the temperature was also sensed exceeds a maximum allowable
value, it can be determined that an oxygen deficiency exists within
the furnace 18. Based on the fluid dynamics within the particular
furnace configuration this oxygen deficiency can be traced back to
one or more burners 28 that are operating without sufficient levels
of oxygen.
[0041] In response to tracing the combustion anomaly back to an
offending burner at step 110 in FIG. 3, the method continues to
include adjusting at least one of a process input and a boiler
configuration affecting combustion of the offending burner at step
115. For instance, if the amount of CO detected by the sensor 38 at
the first common location where the temperature was also sensed
exceeds a maximum allowable value, it can be determined that an
oxygen deficiency exists within the furnace 18. One or more
actuators such as a damper 52 can be adjusted to introduce more
oxygen into the furnace than the amount of oxygen being introduced
in the environment of the offending burner 28 when the combustion
anomaly was detected. The surplus of oxygen can establish a
stoichiometry in the furnace 18 that promotes complete combustion
of the hydrocarbon fuel to produce CO.sub.2 instead of CO.
According to alternate embodiments, a boiler configuration such as
the angle at which an additive is injected into the furnace 18 can
be adjusted at step 115 to bring the operating conditions sensed at
the common location within the furnace 18 within the predetermined
range of acceptable values.
[0042] The adjustment made at step 115 can be recorded at 117 to
develop a real-time data model for correlating future deviations of
the operating conditions sensed at the first common location within
the furnace 18 to particular adjustments of process inputs and/or
boiler configurations. The mathematical model can be updated in
response to each adjustment to reflect the cause and effect of such
adjustments on the operating conditions sensed at the first common
location in the furnace 18 for subsequent iterations to correct
future combustion anomalies.
[0043] To illustrate substantially-uniform operating conditions
across the cross-section of the exhaust port 37 during
substantially-balanced combustion, the exhaust port 37 in FIG. 2
can be divided by two-dimensional grid lines 59 (FIG. 4A) for
purposes of the present method. Dividing the cross-section of the
exhaust port 37 into zones by the grid is conceptual for monitoring
and controlling the combustion performance of the furnace 18, and
not a physical division of the exhaust port 37. The grid dividing
the exhaust port 37 into a plurality of zones is illustrated in
FIGS. 4A-4D, which is a cross section of the exhaust port 37 taken
along line 4-4 in FIG. 2.
[0044] FIG. 4A represents a cross-section of the flue gas exiting
the furnace 18 during a combustion anomaly, wherein the flue gas
exhibits non uniform operating conditions across the cross-section
of the exhaust port 37. The flue gas in FIG. 4A includes many
temperature, CO, combustion or other suitable operating condition
gradients, which are indicated in FIG. 4A by broken lines
designated generally as 60. Each broken line 60 indicates a
combustion gradient, separating regions of the cross section
exhibiting different degrees of combustion. For example, the region
62 enclosed by broken line 64 can include a greater amount of CO in
the flue gas than the region 66 immediately outside of the broken
line 64. For alternate embodiments, the region 62 can represent a
region of the flue gas that has a higher temperature than the
region 66 immediately outside of the broken line 64. In general,
the broken lines 60 separate regions where combustion has
progressed to different stages of completeness.
[0045] The operating conditions of the flue gas exiting via each
zone are affected differently by the combustion of each burner 28
at different spatial locations within the furnace 18. Thus, the
adjustments to the process input and/or boiler configuration
brought about by the method described above with reference to FIG.
3 can be specific to those burners 28 contributing to the
combustion anomalies within the various zones of the exhaust port
37. For example, the region 62 having an unacceptably high CO
concentration defined by broken line 64 in FIG. 4A can be rectified
by adjusting the process input and/or boiler configuration
affecting combustion of the offending burners 28 primarily
contributing to the CO concentration at zones a, b, c and d defined
by the grid. Adjusting the combustion performance of the offending
burners 28 without altering the combustion performance of
non-offending burners minimizes the number of combustion gradients
60 across the cross section of the exhaust port 37.
[0046] The adjustment of the process input and/or boiler
configuration as described with reference to FIG. 3 minimizes
combustion gradients 60 at the exhaust port 37 (FIG. 2) of the
furnace 18. The cross-sectional view of the flue gas leaving the
exhaust port 37 in FIG. 4B following a first iteration of the
method resulting in an adjustment of at least one of the process
input and the boiler configuration. Although the region 62
indicative of the combustion anomaly remains, fewer combustion
gradients indicated by broken lines 60 exist than before the first
adjustment of the process input and/or boiler configuration.
Further, the degree of the combustion gradients may also be less
than the degree of the combustion gradients appearing in FIG. 4A.
For instance, the region 62 in FIG. 4B may represent a CO
concentration of the flue gas that is less than the CO
concentration in the region 62 in FIG. 4A. But just as for FIG. 4A,
the zones a, b, c and d in FIG. 4B where the region 62 is primarily
located correspond to the same offending burners 28 contributing to
the region 62 in FIG. 4A, so further adjustment of the process
input and/or boiler configuration for those offending burners is
appropriate to promote substantially-balanced combustion.
[0047] FIG. 4C illustrates another cross-sectional view of the
combustion gradients for the flue gas exiting the exhaust port 37
of the furnace 18 following another iteration of the method
appearing in FIG. 3. The cross-sectional view in FIG. 4C is
approaching substantially-balanced combustion, and includes a
primary combustion anomaly region 70 defined by the broken line 72
representing a combustion gradient. The primary combustion anomaly
region 70 is present in a greater number of zones (outlined in bold
lines and designated generally a-h) than the region 62 in FIGS. 4A
and 4B. In other words, there are fewer combustion gradients and
more uniform combustion across the cross section of the exhaust
port 37 in FIG. 4C than in FIGS. 4A and 4B, which is indicative of
substantially-balanced combustion. Further adjustment of the
process input and/or boiler configuration will be specific to the
offending burners 28 that are primary contributors to the
combustion anomaly appearing across zones a-h in FIG. 4C.
[0048] Finally, following yet another iteration of the method
described with reference to FIG. 3, substantially-balanced
combustion is achieved and the combustion gradients indicated
generally by broken line 80 in FIG. 4D are minimized. As shown, the
combustion is substantially uniform across a majority of the cross
section of the exhaust port 37. Substantially-balanced combustion
does not necessarily require a complete absence of combustion
gradients, but only that the combustion gradients are minimized
over most of the cross section of the exhaust port 37.
[0049] The invention has been described with reference to the
example embodiments described above. Modifications and alterations
will occur to others upon a reading and understanding of this
specification. Example embodiments incorporating one or more
aspects of the invention are intended to include all such
modifications and alterations insofar as they come within the scope
of the appended claims.
* * * * *