US20110045420A1

US20110045420A1 - Burner monitor and control

Info

Publication number: US20110045420A1
Application number: US12/545,122
Authority: US
Inventors: Michael C. Tanca
Original assignee: Alstom Technology AG
Current assignee: General Electric Technology GmbH
Priority date: 2009-08-21
Filing date: 2009-08-21
Publication date: 2011-02-24
Also published as: EP2467645A2; CA2771507A1; CN102667344A; TW201113481A; KR20120058552A; WO2011022157A2; WO2011022157A3; IN2012DN02376A

Abstract

A monitoring and control apparatus (220) adapted to monitor the combustion of each individual burner (224) in a furnace (1). It includes at least one laser (221) for providing a beam (223) through a flame of a burner (224) in a furnace (1), and at least one detector (222) for detecting the beams (223) after they pass through/near the flame. The monitored signal is passed to an electronics unit (215) that calculates optimum conditions for this burner (224). The electronics unit (215) then causes control unit (214) to adjust the fuel, primary air and secondary air feeds each individual burner (224) to result in a more efficient system that reduces the amount of emissions released.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. Patent Application entitled “OPTICAL FLUE GAS MONITOR AND CONTROL” by the same inventor, Michael Tanca, filed on the same day as the present application. This application incorporates the above-referenced application as if it were set forth in its entirety herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to coal-fired combustion systems, and more particularly to a combustion monitoring system for accurate estimations of system performance of coal-fired combustion systems.
2. Description of the Related Art
In various coal-fired combustion systems, combustion within a combustion system is monitored by a measurement device located in the rear of the furnace. Typically, this is an oxygen sensor. This measurement device provides feedback signals that are used to control the combustion within the combustion system. While such systems work well for controlling aggregate combustion in the furnace, such systems are not responsive to monitoring and controlling the combustion at different burners within the combustion chamber. Therefore, some burners may be working at an optimum level, with one or more performing poorly. This would result in less than optimum performance. It would be advantageous to identify a specific burner or location within the combustion chamber that is not operating well, and only adjust the devices pertaining to that location.
Additional measurement devices provide additional performance, however, it is not feasible to have a large number of measurement devices within a combustion chamber. It is difficult to measure the performance of an individual burner.
In addition, poor control may result from poor sensitivity of the measurement devices. It would be advantageous to have more accurate measurement devices.
Thus, what are needed are methods and apparatus for accurate measurements of individual burners throughout a sampling zone associated with a boiler combustion system. Preferably, the measurements provide for improved control thus leading to improved efficiency.

BRIEF SUMMARY OF THE INVENTION

A burner efficiency system (200) is described for adjusting the operation of individual burner (224) of a tangentially fired furnace (1).
It includes a detector (222) adapted to receive an optical beam (223) and provide an electrical signal corresponding to the optical beam (223) received.
It includes an optical source (221) positioned to create the optical beam (223) that passes through a sampling zone (8) and crosses a trajectory (42) just above of a flame emanating from an individual burner (224) and impinges upon the detector (223).
An electronics unit (214) is adapted to receive the signal created by the detector (222) and identify at least one physical property of material between the optical source (221) and detector (222). The electronics unit (214) creates an adjustment signal indicating parameters of the individual burner that should be adjusted to optimize the operation of this individual burner (224).
Some of the parameters that may be adjusted are secondary airflow rate into the furnace (1), primary airflow rate into the furnace (1), and fuel flow rate into the furnace (1).
It may also be embodied as an apparatus (200) for monitoring a property of at least one constituent in flue gas from a furnace (1), the apparatus having an optical monitoring system (220) comprising at least one optical source (221) adapted to provide an optical beam (223) through flue gasses substantially produced by a single burner (224) of a furnace (1).
It includes at least one detector (222) adapted to detect the optical beam (223) and provide a monitored signal to an electronics unit (215). The electronics unit (215) configured to estimate a property of at least one constituent in the sampling zone and create an adjustment signal to adjust the operation of said furnace (1).
It may be further embodied as a method for adjusting the operation of individual burner (224) of a tangentially fired furnace (1). The steps include creating an optical beam (223) that passes through a sampling zone (8) and crosses a trajectory (42) of a flame emanating from an individual burner (224) and impinges upon a detector (223).
The optical beam (223) is sensed at the detector to create an electrical signal corresponding to the optical beam (223) received.
At least one physical property of material in the sampling zone (8) is identified from the created electrical signal.
The identified physical properties are compared to a predetermined desired level.
Adjustments to a set of burner parameters are calculated from the comparison that would cause the identified physical property to adjust toward the predetermined desired level.
The burner parameters of the individual burner are adjusted according to the calculated adjustments to optimize the operation of the individual burner (224).

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 depicts a cross-sectional schematic diagram of a prior art furnace;

FIG. 2 depicts a plan view of prior art combustion monitoring system;

FIG. 3 depicts a cross-sectional schematic diagram of an embodiment of a furnace according to the present invention;

FIG. 4 depicts a plan view of an embodiment of a combustion monitoring system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed is a method and apparatus for providing for accurate monitoring of combustion conditions, flue gas constituents from a combustion system and controlling the combustion system based upon the monitoring. In various non-limiting embodiments provided herein, the combustion system is a solid fuel, gaseous or liquid fuel fired combustion system. The combustion system may be a combination furnace and boiler, or steam generator. One skilled in the art will recognize, however, that the embodiments provided are merely illustrative and are not limiting of the invention.
The methods and apparatus make use of optical detection systems. As provided herein, the optical signaling and detection systems are simply referred to as a “monitoring system.” In general, the monitoring system includes a variety of components for performing a variety of associated functions. The components may include a plurality of lasers, a plurality of sensors, a control unit, computer components, software (i.e., machine executable instructions stored on machine readable media), signaling devices, motor operated controls, at least one power supply and other such components. The monitoring system provides for a plurality of measurements of at least one gas constituent relative to a sampling zone. The plurality of measurements provide for, among other things, measurement of gas constituents in the sampling zone, such as in relation to a burner (i.e., a nozzle). The measurements may be performed in multiple locations by use of laser technology, thus providing a localized, more responsive measure of fuel combustion. Of course, the monitoring system may also be viewed as a control system. More specifically, measurement data from the monitoring system may be used to control aspects of the combustion system. Accordingly, for at least this reason, the monitoring system may be considered as a control system or at least as a part of a control system.
Turning now to FIG. 1, there is shown a side view of a prior art furnace 1. The furnace 1 includes a monitoring system 120. In this rudimentary example, the monitoring system 120 includes a plurality of optical sources 121 which may be lasers. The optical sources 121 provide optical beams 123 which are detected by a corresponding plurality of detectors 122. The detectors 122 are coupled to an electronics unit 115 to provide for characterization of received optical signals. The electronics unit 115 provides for estimations of physical aspects of the sampling zone 8 between the optical sources 121 and the corresponding detector 122. These physical aspects may include composition or abundance of gas constituents. The estimations may be performed using techniques as are known in the art.
Turning to FIG. 2, further aspects of a prior art monitoring system 120 are shown. In this example, the monitoring system 120 has a plurality of optical sources 121 and a plurality of detectors 122. The optical sources 121 form a grid of optical beams 123. The optical beams 123 are detected by the detectors 122. The optical beams 123 are aligned in a grid pattern with intersecting beams as shown. Each of the burners 124 are downstream of the fuel feed, primary air feed and secondary air feed (105, 106, 107, respectively of FIG. 1) and provide a mixture of fuel and air to the combustion chamber (2 of FIG. 1).
The term “sampling zone” 8 refers to portion of a combustion chamber 2 monitored by the monitoring system 120.
The prior art arrangement shown in FIG. 2, show a plurality of wall-mounted burners 24 which provide combustion in a grid arrangement as depicted. Similarly, a plurality of lasers 121 and detectors 122 are arranged in a similar fashion. Since the flames of each nozzle 24 overlap, the detector system 120, cannot detect the functioning of each individual burner 24. Therefore, any adjustments must be made on the overall system, affecting all burners 24. There is no ability to monitor and adjust individual burners 24.
FIG. 3 depicts a cross-sectional schematic diagram of an embodiment of a furnace 1 according to the present invention. The furnace 1 includes a plurality of monitoring systems 220, each for monitoring an individual burner 224, as opposed to the prior art.
It also includes a plurality of control units 224 which control the secondary air feed 207, and optionally, the fuel feed 205 and the primary air feed 206 for each individual burner 224, as opposed to the prior art.
Each monitoring system 220 includes at least one optical source 221 which may be a laser. The optical sources 221 provide optical beams 223 which are detected by a corresponding plurality of detectors 222. Each beam passes through a single burner flame or just above a flame to minimize optical scattering, indicated by a trajectory (42 of FIG. 4). Please note that beam 223 passes through the burner flame at an oblique angle that is difficult to depict in this elevational view.
Solid coal particles are being blown out of the burners 224 which quickly burn into gases inside of the combustion chamber. These coal particles scatter and weaken the optical beam 223 resulting in insufficient intensity being received by the detector 222. In this case, the optical beam 223 and detector 222 must be located just above the flame trajectory 42 where the coal particles are no longer present. This provides a sufficient beam 223 that now can be detected at the detector 222 after it intersects flame trajectory 42 at point 45. In this case, it is above the flame.
Please note that the optical beam 223 may be adjusted by adjusting optical source 221 and detectors 222 such that beam 223 passes through sampling region 8 and passes through flame trajectory 42 at point 45. Flame trajectory 42 may pass through the flame emitted from the burner 224 or may pass slightly above this flame such that most of the solid coal particles are burned off at that location.
The locations of any of the detector 222 and optical source 221 pairs are interchangeable to allow them to be located on either end of beam 223.
Each detector 222 is coupled to its corresponding electronics unit 215 to provide for characterization of received optical signals for each burner 224. Each electronics unit 215 provides for estimations of physical aspects of the sampling zone 8 between the optical sources 221 and the corresponding detector 222. These physical aspects may include composition or abundance of gas constituents. The estimations may be performed using signal attenuation, signal absorption, fluorescence and other forms of wavelength shifting, scatter and other such techniques.
Even though only a single burner 224, optical source 221 and detector 222 are shown here, it is to be understood that there may be multiple burners 224, optical sources 221 and detectors 222 at various levels of the furnace 1. These may also be arranged obliquely with reference to a horizontal and/or vertical axis, and the burners need not be arranged in groups.
FIG. 4 shows one embodiment of the present invention adapted to a tangentially-fired furnace 1 having the plurality of burners 224 located at the periphery of the combustion chamber 2. Each burner 224 is aimed toward a periphery of an imaginary circle where a fireball 9 will occur once combustion begins. This design causes a fireball 9 to be created having a circular swirling pattern, as is typical for tangentially-fired furnaces.
For a least one burner 224, the optical source 222 is aimed such that its beam 223 crosses a single flame trajectory 42 at a point 45. The laser beam 223 is monitored by a detector 223 to measure absorption and transmission at various wavelengths. This allows an analysis of various gas species and temperatures at the intersection point 45 of the flame from a single burner 224.
The point 45 where the flame trajectory 42 crosses the beam 223 should be equal for all burners 224 for accurate, comparable measurements.
By providing such a setup at each of the burners 224, a combustion monitoring system 220 may be constructed.
Point 45 monitored is the same distance from the burner 224 for all burners 224. Since the flame trajectory 42 is uninterrupted or contaminated by another lateral burner 224 at a given level, this geometry provides independent measurement of the functioning of each burner 224. There is no external measurement from other burner flames from each reading. This provides a more accurate measurement of each individual burner 224.
In this example, beams 223 can be located at the level of the burners 224 or slightly above or below the burner 224 to give the strongest discrimination of gas species measurement by optical sources 221.
As indicated above the optical sources 221, detectors 222 and beams 223 may be adjusted to optimize the readings. They also may be angled upward or downward, or have adjustable means for modifying their angles.
The present invention provides for measurement and assessment of gas species such as CO, CO₂and O₂an unburned fuel present in the combustion chamber 2. Optionally, it may also detect a number of other entities, such as SO₂, SO₃, NO₂, NO₃and Hg.
Referring now to both FIGS. 3 and 4, the monitored signal from each detector 222 may then be fed back to the electronics unit 215 to calculate optimum fuel, primary airflow and secondary air flow. This is fed to the control unit 214 of each burner 224 to control the fuel flow 205, primary air feed 206, and secondary air feed 207. These may be regulated with common devices such as air dampeners, valves and other flow controls.
For convenience of explanation, the monitoring system 220 may be regarded as producing “measurement data,” “monitoring data,” “characterization data” and the like. The combination of the monitoring system 220 and the control unit 214 results in a monitoring and control system 200.
Having thus described aspects of the monitoring and control system 200, one skilled in the art will recognize that features of merit in the invention include, without limitation: use of a grid of lasers directly above the burner level to measure gas species for both tangential fired and wall fired furnace arrangements; an alternative grid design for tangential fired furnaces that can be used at each burner level or above each burner level that measures gas species at a given location in the flame to control the local burner stoichiometry; ability to control localized combustion within the furnace using laser grid measurement through air flow biasing between burners as a secondary control of combustion; primary control of boiler combustion using lasers at the furnace outlet to control air feeds to the burners; an improved, non-grid design to measure gas species at the flue gas outlet; control of downstream pollution control systems using laser grid measurements; use of localized laser gas species measurements in or around the burner area to control the combustion and fuel air dampers for individual burner stoichiometry control; control of all boiler and environmental controls using a coordinated control system having laser gas species measurements as an input; that can feedback to the control system for burner control and/or pollution control on a plant performance and economics basis.
The optical sources may be any lasers that transmit light in a band useful in detecting desired constituents in the flue gasses. This may include lasers of all types of gasses and species. Detection techniques may be based on modulation of signal frequency or signal wavelength as well as signal attenuation. In general, embodiments of the monitoring system 220 include apparatus that measure gas concentrations by shining the laser beam through a sample of gas and measuring the amount of laser light absorbed. However, the optical source and detector wavelengths can be tuned to detect absorption at a variety of wavelengths. These properties give laser detectors a good combination of properties, including selectivity and sensitivity.
Advantages of laser monitoring include an ability to characterize the gas constituents. That is, a tunable laser generally emits light in the near infrared (NIR) region of the electromagnetic spectrum. Many of the combustion gases absorb light in NIR, and may be characterized by a number of individual “absorption lines.” A tunable laser can be tuned to select a single absorption line of a target gas, which does not overlap with absorption lines from any other gases. Therefore, laser gas sensing can be considered selective with regard to sampling of gases. A variety of other technical advantages is known to those skilled in the art. Further, tunable lasers are relatively inexpensive. Accordingly, the monitoring system 220 is cost effective and easy to maintain.
Exemplary tunable lasers are produced by Aegis Semiconductors, Inc. of Woburn, Mass. One non-limiting example of a thermally tunable optical filter is disclosed in the U.S. Patent Application Publication No.: US/2005/0030628 A1, entitled “Very Low Cost Narrow Band Infrared Sensor,” published Feb. 10, 2005, the disclosure of which is incorporated by reference herein in it's entirety. This application provides an optical sensor for detecting a chemical in a sample region that includes an emitter for producing light, and for directing the light through the sample region. The sensor also includes a detector for receiving the light after the light passes through the sample region, and for producing a signal corresponding to the light, the detector receives. The sensor further includes a thermo-optic filter disposed between the emitter and the detector. The optical filter has a tunable passband for selectively filtering the light from the emitter. The passband of the optical filter is tunable by varying a temperature of the optical filter. The sensor also includes a controller for controlling the passband of the optical filter and for receiving the detection signal from the detector. The controller modulates the passband of the optical filter and analyzes the detection signal to determine whether an absorption peak of the chemical is present.
One skilled in the art will recognize that the foregoing is merely one embodiment of the laser 221, and that a variety of other embodiments may be practiced. Accordingly, it should be recognized that the term “optical” makes reference to any wavelength of electromagnetic radiation useful for practice of the teachings herein. In general, the electromagnetic radiation may include a wavelength, or band of wavelengths that are traditionally considered to be at least one of microwave, infrared, visible, ultraviolet, X-rays and gamma rays. However, in practice, the wavelength, or band of wavelengths selected for an optical signal are generally classified as at least one of infrared, visible, ultraviolet, or sub-categories thereof.
Further, one should recognize that the laser 221 generally provides light amplification by stimulated emission of radiation. That is, a typical laser emits light in a narrow, low-divergence monochromatic beam with a well-defined wavelength. However, such as restriction is not necessary for practice of the teachings herein. In short, any optical beam that exhibits adequate properties for estimating measurement data may be used. Determinations of adequacy may be based upon a variety of factors, including perspective of the designer, user, owner and others. Accordingly, the laser 21 need not precisely exhibit lasing behavior, as traditionally defined.
The monitoring system 220 may be provided as part of a retrofit to existing combustion systems. For example, the monitoring system 220 may be mounted onto existing components and integrated with existing controllers. Accordingly, a system making use of the teachings herein may also include computer software (i.e., machine readable instructions stored on machine readable media). The software may be used as a supplement to existing controller software (and/or firmware) or as an independent package.
Further, a kit may be provided and include all other necessary components as may be needed for successful installation and operation. Example of other components include, without limitation, electrical wiring, power supplies, motor and/or manually operated valves, computer interfaces, user displays, assorted circuitry, assorted housings, relays, transformers, and other such components.
Accordingly, provided is a combustion system that includes at least one laser based detector at the boiler outlet to measure the gas species, such as oxygen. The purpose of both systems in both locations is, among other things, to control the overall air flow to the boiler with the laser at the boiler outlet and to provide a local control of the boiler burners with the use of the lasers mounted proximate to each burner.
Software may be used in the functioning and operation of various parts of the present invention. For example, electronics unit (215 of FIGS. 3, 4) and control unit of FIGS. 1, 3 may employ such software. This software may be provided in conjunction with a computer readable medium, may include any type of media, such as for example, magnetic storage, optical storage, magneto-optical storage, ROM, RAM, CD ROM, flash or any other computer readable medium, now known or unknown, that when executed cause a computer to implement the method and operate apparatus of the present invention. These instructions may provide for equipment operation, control, data collection and analysis and other functions deemed relevant by a user.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A burner efficiency system (200) for adjusting the operation of individual burner (224) of a tangentially fired furnace (1) comprises:

a detector (222) adapted to receive an optical beam (223) and for provide an electrical signal corresponding to the optical beam (223) received;

an optical source (221) positioned to create an optical beam (223) that passes through a sampling zone (8) and crosses a trajectory (42) of a single flame emanating from an individual burner (224) and impinges upon the detector (223);

an electronics unit (214) adapted to receive the signal created by the detector (222) and identify at least one physical property of material between the optical source (221) and detector (222) and create an adjustment signal indicating parameters of said individual burner that should be adjusted to optimize the operation of this individual burner (224).

2. The burner efficiency system (200) of claim 1, wherein said parameters are selected from the group consisting of:

a secondary air flow rate into the furnace (1),

a primary air flow rate into the furnace (1), and

a fuel flow rate into the furnace (1).

3. The burner efficiency system (200) of claim 1, further comprising:

a secondary air feed (207) for providing additional combustion air to said furnace (1);

a control unit (214) coupled to the electronics unit (215), and to the secondary air feed adapted to adjust the amount of air provided to the burner (224) based upon the adjustment signal provided by the electronics unit (215).

4. The burner efficiency system (200) of claim 3, further comprising:

a fuel feed (105) coupled to the control unit (214), the fuel feed adapted to provide solid fuel particles to the furnace (1);

a primary air feed (206) coupled to the control unit (214), the primary air feed adapted to provide air to entrain sold fuel particles and carry them into the furnace (1); and

wherein the control unit is further adapted to regulate the fuel feed (205) and primary air feed (206 to adjust the amount of fuel particles and primary air provided to furnace (1) based upon the adjustment signal received form electronics unit (215).

5. The burner efficiency system (200) of claim 1 wherein the optical source (221) is a laser, and the detector (222) is adapted to sense laser light.

6. The burner efficiency system (200) of claim 1 wherein the physical property identified comprises one of the group consisting of:

temperature, oxygen (02) concentration, carbon monoxide (CO) concentration, carbon dioxide (CO₂) concentration, water vapor concentration, sulfur dioxide (SO₂) concentration, sulfur trioxide (SO₃) concentration, nitrogen dioxide (NO₂) concentration, nitrogen trioxide (NO₃) concentration, mercury (Hg) concentration, unburned hydrocarbon concentration and unburned fuel concentration.

7. The burner efficiency system (200) of claim 1 wherein the optical beam (223) crosses the flame trajectory (42) an intersection point (45).

8. The burner efficiency system (200) of claim 1 wherein the distance from the intersection point 45 to its corresponding burner (224) is the same for all burners (224).

9. The burner efficiency system (200) of claim 1 wherein there are a plurality of burners (224) on multiple levels of furnace 1, and there is a plurality of an optical sources (221) each positioned to create an optical beam (223) crosses a trajectory (42) of a flame emanating from a single burner (224) and impinges upon a detector (223).

10. An apparatus (200) for monitoring a property of at least one constituent in flue gas from a furnace (1), the apparatus comprising:

an optical monitoring system (220) comprising at least one optical source (221) adapted to provide an optical beam (223) through flue gasses substantially produced by a single burner (224) of a furnace (1), and

at least one detector (222) adapted to detect the optical beam (223) and provide a monitored signal to an electronics unit (215),

the electronics unit (215) configured to estimate a property of at least one constituent in the sampling zone and create an adjustment signal to adjust the operation of said furnace (1).

11. The apparatus (200) as in claim 10, wherein the at least one laser (121) comprises a semiconductor tunable optical laser.

12. The apparatus (200) as in claim 10, wherein the constituent comprises at least one of CO, CO₂, Hg, SO₂, SO₃, NO_x, O₂, Hg and unburned fuel.

13. The apparatus (200) as in claim 10, wherein the property comprises at least one of a presence, a quantity, a density, a concentration of said constituent and a rate of change of any of these properties.

14. The apparatus (200) as in claim 10, further comprising a control unit (214) adapted to receive the adjustment signal and control the furnace (1).

15. The apparatus (200) as in claim 14, wherein the control unit (214) is configured to control a flow of at least one of a fuel feed (205), a primary air feed (206) and a secondary air feed (207) to said furnace (1).

16. The apparatus (200) as in claim 10, comprising a plurality of lasers (221) for providing a plurality of beams (223) and a plurality of detectors (222) for detecting the plurality of beams (223).

17. The apparatus (200) as in claim 10, wherein the plurality of lasers (221) and the plurality of detectors (222) are arranged for monitoring a tangentially-fired furnace (1).

18. The apparatus (200) as in claim 10, wherein the electronics unit (215) comprises machine executable instructions stored on machine-readable media, the instructions comprising instructions for:

estimating a property of the at least one constituent;

determining an adjustment signal from the estimated property to cause the estimated property to become closer to a predetermined value; and

providing an adjustment signal to the control unit (214).

19. The apparatus (200) as in claim 18, further comprising instructions for modulating the optical signal.

20. The apparatus (200) as in claim 10, wherein the beams (223) pass through two or three dimensions of the combustion system (1).

21. A method for adjusting the operation of individual burner (224) of a tangentially fired furnace (1) comprising the steps of:

creating an optical beam (223) that passes through a sampling zone (8) and crosses a trajectory (42) of a flame emanating from an individual burner (224) and impinges upon a detector (223);

sensing the optical beam (223) at the detector;

creating an electrical signal corresponding to the sensed optical beam (223);

identifying at least one physical property of material in the sampling zone (8) from the created electrical signal;

comparing the identified physical properties to a predetermined desired level;

calculating adjustments of a set of burner parameters that would cause the identified physical property to adjust toward the predetermined desired level;

adjusting the burner parameters of the individual burner according to the calculated adjustments to optimize the operation of the individual burner (224).

22. The method as in claim 21, wherein at least one of the identifying and the adjusting is performed on a real-time basis.