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CA2014635A1 - Method and means for measuring the oxygen content of flue gas in a boiler - Google Patents

Method and means for measuring the oxygen content of flue gas in a boiler

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Publication number
CA2014635A1
CA2014635A1 CA 2014635 CA2014635A CA2014635A1 CA 2014635 A1 CA2014635 A1 CA 2014635A1 CA 2014635 CA2014635 CA 2014635 CA 2014635 A CA2014635 A CA 2014635A CA 2014635 A1 CA2014635 A1 CA 2014635A1
Authority
CA
Canada
Prior art keywords
furnace
improvement
flue gas
measuring
oxygen content
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA 2014635
Other languages
French (fr)
Inventor
Claud B. Heuszel
Claude L. Davis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Zircoa Inc
Gulf States Utilities Co
Original Assignee
Zircoa Inc
Gulf States Utilities Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Zircoa Inc, Gulf States Utilities Co filed Critical Zircoa Inc
Publication of CA2014635A1 publication Critical patent/CA2014635A1/en
Abandoned legal-status Critical Current

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  • Regulation And Control Of Combustion (AREA)

Abstract

ABSTRACT OF THE DISCLOSURE
The oxygen content in a flue gas generated in a furnace of a boiler having pressurized areas and employed for controlling the air/fuel ratio at burners of the furnace as a function of the measured flue gas oxygen content is measured. This measurement is carried out by at least one high-temperature oxygen-measuring probe located within the furnace itself and/or adjacent a furnace outlet of the furnace.

Description

OF FLUE GAS IN A BOILER

BACKGROUND OF THE INVENTION
The present invention relates to a method and means for measuring the oxygen content in a flue gas generated in a furnace of a boiler having pressurized areas and for controlling the air/fuel ratio at burners of the furnace as a function of the measured flue gas oxygen content. More particularly, the present invention relates to such a method and means employed in a boiler for steam production for various purposes, for example for power generation such as generation of electrical power.
In boilers of the above type, a burner or burners of a furnace are supplied with air and fuel that are combusted to form a flue gas that is passed to a heat exchanger of the boiler for generation of steam. It is known to measure the oxygen content of the flue gas within the boiler installation to determine whether there has been an effective combustion of the fuel with the least possible air supply. Thus, detection of the lowest possible oxygen surplus in the flue gas is an indication of an efficient combustion process. The air/fuel ratio at or supplied to the burners is adjusted as a function of the detected or measured oxygen content of the flue gas.
Measuring of the oxygen content in the flue gas has been achieved in the past in a low temperature area of the boiler, for example in an opening after the flue gas has been supplied to a heat exchanger of the boiler. It has been determined however that measured values of oxygen content in the flue gas determined in this manner are subject to considerable uncontrollable variations. Due to the fact that, due to leakages in the installation, air is infiltrated into the system from the higher pressure areas into the flue gas during its passage from 1.

~014635 ~
-.he furnace through the boiler, for example to a preheater or er~nomizer. This particularly is true in the case of a boiler h~ving areas at a higher pressure than in the furnace. This leads to inaccurate measurements of up to 2~ oxygen content compared to the actual content of oxygen in the flue gas.
Additionally, the degree of error can vary due to varying pressure differences between the furnace area and pressurized seal areas of the boiler.

SUMMARY OF THE_ INVENTION
With the above discussion in mind, it is an object of the present invention to provide an improved method and means for measuring the oxygen content in flue gas generated in a furnace of a boiler having pressurized areas and for controlling the air/fuel ratio at burners of the furnace as a function of the measured flue gas oxygen content, whereby it is possible to overcome the above and other disadvantages of the prior art.
It is a further object of the present invention to provide such a method and means whereby measurement of the oxygen content in the flue gas is possible in a simple, trouble free and reliable manner.
It is a still further object of the present invention to provide such a method and means that is capable of simple installation, calibration and maintenance.
The above and other objects are achieved in accordance with the present invention by the measurement of the flue gas oxygen content by means of at least one high-temperature oxygen-measuring probe located within the furnace itself and/or adjacent a furnace outlet of the furnace, i.e. within a high temperature area within or near the furnace.
In this manner it is possible to achieve at the same t'~e a number of surprising advantages, compared with prior art systems.
Thus, the measuring probe responds extremely rapidly to variations in the oxygen contenit so that the air/fuel ratio at the burners of the furnace can be adjusted immediately as a function of the measurement. Because a high-temperature measuring probe is employed in the present invention, the probe can be located within a radiant area or region of the furnace, that is in a region thereof that is at a temperature of as high as approximately 600 to 1600C. Such temperatures are above the critical combustion temperature. Accordingly, in such area the full amount of fuel that will be burnt has been burnt, and the oxygen content measured at such area thereby will provide reliable information as to optimized combustion efficiency and improve boiler efficiency. If, for example, when a minimum oxygen content is measured, then it can be assured, in accordance : ~.
~`~ with the present invention, that the air/fuel ratio is optimized.

~ The type and application of the measuring probe il according to the present invention has the further advantage that 1 flue gas does not need to be removed from the flue gas channel or J
passageway in the boiler for conducting measuring. Additionally, in accordance with the present invention it is not necessary to heat the measuring probe prior to measurement. Due to the above features of the present invention, it is possible to eliminate pumps and supplementary heaters that have been necessary in prior art installations.
Furthermore, due to the above features of the present lnvention it is possible to ensure that the oxygen content has been measured with regard to flue gas that has not had added thereto uncontrolled amounts of air, for example drawn into the installation from the outside, as is the case in prior art installations. In this manner, reliability of the measurements is improved remarkably. 3 ; , ', . .

: 201463~
The measuring probe can be located, as indicated above, a radiant section or area of the furnace. Also, the probe can be located within the furnace outlet of the furnace or adjacent thereto. Furthermore, the probe can be located adjacent a heat exchanger, for example a superheater, of the boiler. In accordance with a particularly preferred arrangement of the present invention, there are provided a plurality of measuring : .
probes. Such plurality of probes may be located in the above discussed areas and/or in all of such areas. The provision of a plurality of probes ensures that measurement will continue even if one of the probes should fail. Additionally, measurement of the oxygen content and regulation of the air/fuel ratio of the burners is even more reliable by controlling the air/fuel ratio by a control signal generated by an average value or a median value from the signals from the plurality of probes. Still further in accordance with the present invention, it is possible to control the air/fuel ratio of ~he burners by employing a control signal indicating the lowest oxygen content from among the signals generated by the plurality of probes. In this manner it is possible to prevent so-called "smoking" or "fuming" at the burners.
One skilled in the art would understand various types of probes or measuring devices that could be employed for `
carrying out the present invention, i.e. probes capable of ~..... .
measuring oxygen content at the high temperatures contemplated by the present invent~on. One possible such probe may be a zirconium-oxide analyzer. However, this is intended to be exemplary only, and not limiting, since one skilled in the art ~ readily would be able to determine other probes employable in `~ carrying out the present invention.

Furthermore, the present invention can be employed for ~ boilers fueled by various known fuels, for example coal dust or ,j y : !,3 .

::` ' : : -~01463~
various combustible gases. Similarly, it is to be understood lt the use of the term "air" is intended to refer to, as is known in the art, oxygen, air or other oxygen-containing gases.
Furthermore howe~er, thc basic conccpt of the present invention can be employed wit~. other types of operational heating installations.

: " .
,'.~
. BRIEF DESCRIPTION OF THE DRAWING
Other objects, features and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment thereof, with reference to the accompanying drawing, wherein:
The single figure is a representation of a typical boiler installation adapted to the method and means of the , present invention.
i i!
~. ., DETAILED DESCRIPTION OF THE INVENTION
The drawing illustrates a representation of a typical boiler, indicated generally at 10, intended for the generation of steam. Boiler 10 includes, as is known, a furnace 12 having therein at least one burner 14 supplied with air, for example from a source 16 that may be any conventionally known such source or regulator for supplying air, and also with a known fuel. The air and fuel are combusted in furnace 12 to generate a flue gas that is supplied from the furnace outlet to a heat exchanger, for example a superheater 18, of the boiler, for example for the generation of steam. The flue gas has heat therefrom withdrawn at the heat exchanger and then passes, for example, through a preheater 20 and an air heater 22 to be directed therefrom for any known purpose or to any known position of utilization.
````~ S

Within the furnace 12, for example within a radiant se^'ion 24 thereof, or adjac~nt a furnace outlet 26 ther~of, or adjacent heat exchanger 18, is located at least one high-temperature oxygen-measurin~ probe 28. Preferably, as illustrated in the drawing, a plurality of probes 28 are provided.
Due to the location of the probes 28 in high-temperature regions, the probes are very sensitive to even slight variations in oxygen in the flue gas and are capable of very rapidly detecting and generating signals representative of such oxygen content changes. The probes generate signals that are employed to regulate the air/fuel ratio at the burners 14, for example by regulating the air supply to the burners. For example, signals generated by probes 28 can be supplied to a controller, for example as shown at 30, capable of processing such signals and generating a control signal to source 16. In this manner, the air supply or air regulating device, or individual air regulating devices of the burners may be Gontrolled as a function of the oxygen content measurements of the probes 28.
The above features are illustrated only in the drawing, and it is contemplated that any known and conventional manner of regulating the air/fuel ratio that would be well understood by one skilled in the art could be employed in carrying out the . ~
present invention.
It furthermore is to be understood that probes 28 can ~`~ be any type of known detector or analyzer capable of determining `~ oxygen content in the high temperature atmosphere contemplated.
Those skilled in the art readily would be able to determine the types of elements that could be used for probes 28.
Although the present invention has been described and illustrated with respect to preferred features thereof, it is ~ G

201463~ -: to be understood that various changes and modifications may be made to the specifically described and illustrated features . without departing from the scope of the present invention.

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Claims (16)

1. In a method for measuring the oxygen content in a flue gas generated in a furnace of a boiler having pressurized areas and for controlling the air/fuel ratio at burners of said furnace as a function of the measured flue gas oxygen content, the improvement comprising:
measuring said flue gas oxygen content by means of at least one high-temperature oxygen-measuring probe within said furnace and/or adjacent a furnace outlet of said furnace.
2. The improvement claimed in claim 1, comprising conducting said measuring within a radiant section of said furnace.
3. The improvement claimed in claim 1, comprising conducting said measuring within said furnace outlet.
4. The improvement claimed in claim 1, wherein said boiler includes a heat exchanger to which said flue gas passes from said furnace outlet, and comprising conducting said measuring adjacent said heat exchanger.
5. The improvement claimed in claim 4, wherein said heat exchanger is a superheater.
6. The improvement claimed in claim 1, comprising conducting said measuring by means of a plurality of said probes.
7. The improvement claimed in claim 6, wherein said controlling comprises employing a control signal generated by averaging signals from said plurality of probes for regulating said air/fuel ratio.
8. The improvement claimed in claim 6, wherein said controlling comprises employing a control signal indicating the lowest oxygen content from among the signals generated by said plurality of probes for regulating said air/fuel ratio.
9. The improvement claimed in claim 1, wherein said probe comprises a zirconium-oxide analyzer.
10. In a boiler including pressurized areas, a furnace having burners for combusting an air/fuel mixture for generating flue gas, and means for measuring the oxygen content of said flue gas for controlling the air/fuel mixture at said burners as a function of the measured flue gas oxygen content, the improvement wherein said means comprises:
at least one high-temperature oxygen-measuring probe located within said furnace and/or adjacent a furnace outlet of said furnace.
11. The improvement claimed in claim 10, wherein said probe is located within a radiant section of said furnace.
12. The improvement claimed in claim 10, wherein said probe is located within said furnace outlet.
13. The improvement claimed in claim 10, wherein said boiler includes a heat exchanger to which said flue gas passes from said furnace outlet, and said probe is located adjacent said heat exchanger.
14. The improvement claimed in claim 13, wherein said heat exchanger comprises a superheater.
15. The improvement claimed in claim 10, wherein said means comprises a plurality of said probes.
16. The improvement claimed in claim 10, wherein said probe comprises a zirconium-oxide analyzer.
CA 2014635 1989-04-24 1990-04-17 Method and means for measuring the oxygen content of flue gas in a boiler Abandoned CA2014635A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US34195489A 1989-04-24 1989-04-24
US07/341,954 1989-04-24

Publications (1)

Publication Number Publication Date
CA2014635A1 true CA2014635A1 (en) 1990-10-24

Family

ID=23339713

Family Applications (1)

Application Number Title Priority Date Filing Date
CA 2014635 Abandoned CA2014635A1 (en) 1989-04-24 1990-04-17 Method and means for measuring the oxygen content of flue gas in a boiler

Country Status (1)

Country Link
CA (1) CA2014635A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102095773B (en) * 2009-12-09 2013-06-26 华北电力科学研究院有限责任公司 Smoke oxygen content measurement method and system
CN112763648A (en) * 2020-11-25 2021-05-07 华能国际电力股份有限公司德州电厂 Method for measuring flue gas atmosphere of hearth of lean coal boiler

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102095773B (en) * 2009-12-09 2013-06-26 华北电力科学研究院有限责任公司 Smoke oxygen content measurement method and system
CN112763648A (en) * 2020-11-25 2021-05-07 华能国际电力股份有限公司德州电厂 Method for measuring flue gas atmosphere of hearth of lean coal boiler

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