Data processing: measuring – calibrating – or testing – Calibration or correction system – Fluid or fluid flow measurement
Reexamination Certificate
2003-02-18
2004-02-10
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Fluid or fluid flow measurement
C702S182000
Reexamination Certificate
active
06691054
ABSTRACT:
This invention relates to a fossil-fired power plant or steam generation thermal system, and, more particularly, to a method for determining its heat rate from the total effluents flow, the EPA's F Factor and other operating parameters. It further teaches how the F Factor may be used to determine the system's emission rates of pollutants from fossil combustion.
BACKGROUND OF THE INVENTION
The importance of determining a fossil-fired power plant's or steam generation system's heat rate (inversely related to thermal efficiency) is critical if practical day-to-day improvements in heat rate are to be made, and/or problems in thermally degraded equipment are to be found and corrected. Although elaborate analytical tools are sometimes needed, simpler and less expensive methods are also applicable which do not require high maintenance nor the input of complex operational system data, and, also, whose accuracy is not greatly compromised. Both the F Factor and the L Factor methods address this need.
General background of this invention is discussed at length in spplication Ser. No. 09/273,711 (hereinafter denoted as '711), and in application Ser. No. 09/047,198 (hereinafter denoted as '198). In '711 the L Factor is termed the “fuel factor”.
As discussed in '711, related artto the present invention was developed by Roughton in 1980; see J. E. Roughton, “A Proposed On-Line Efficiency Method for Pulverized-Coal-Fired Boilers”, Journal ofthe Institute of Energy, Vol.20, March 1980, pages 20-24. His approach using the L Factor (termed M
d
/I
d
in his work) in developing boiler efficiency was to compute system losses such that &eegr;
Boiler
=1.0−&Sgr; (System Losses). This is a version of the Heat Loss Method discussed in '711. The principle losses he considered were associated with dry total effluents (termed stack losses), effluent moisture loss and unburned carbon loss. Roughton's method produces boiler efficiency independent of any measured fuel flow and independent of any measured total effluents flow.
Related art known to the inventor since '711 and '198 were filed is the technical paper: S. S. Munukutla, “Heat Rate Monitoring Options for Coal-Fired Power Plants”,
Proceedings of Heat Rate Improvement Conference
, Baltimore, Md., sponsored by Electric Power Research Institute, September 1998. In this paper Munukutla explains 40 CFR Part 60, Appendix A, Method 19, and the use of its F Factor to determine heat rate. Munukutla makes no mention of correction factors, neither conceptual nor those associated with measurement error. He concludes “. . . that the heat rate, as determined bythe F-factor method, is in error by at least 10-20%.” In his “Conclusions” section, Munukutla states that: “The F Factor method may give accurate results, provided the stack gas flow rate and CO
2
concentration can be measured accurately.” He makes no mention of the molecular weight, or assumed composition, of the total effluents from combustion. Further, Munukutla explicitly states in his writing and by equation that system heat rate is inversely proportional to the concentration of effluent CO
2
.
Other related art is the technical presentation by N. Sarunac, C. E. Romero and E. K. Levy entitled “F-Factor Method for Heat Rate Measurement and its Characteristics”, presented at the Electric Power Research Institute's (EPRI) Twelfth Heat Rate Improvement Conference, Jan. 30 to Feb. 1, 2001, Dallas, Tex. and available from the proceedings (EPRI, Palo Alto, Calif.). This work discusses the CO
2
based F
C
Factor and the O
2
based F
D
Factor and their use in determining system heat rate. They stated that the F Factor method is not used due to its low precision and accuracy, siting 5 to 25% error compared to conventional heat rate methods. The authors site the principal sources of error as being the flue gas flow rate, and either the CO
2
concentration or the O
2
concentration measurement in the effluent. They discuss methods of improving the measurement accuracy of these quantities. These authors also indicate by equation that heat rate is inversely proportional to the concentration of effluent CO
2
or O
2
.
Related art to the present invention also includes the EPA's F Factor method, discussed in '711, and whose procedures are specified in Chapter 40 of the Code of Federal Regulations (40 CFR), Part 60, Appendix A, Method 19. Assumed by Method 19 is that an F
C
, F
D
or F
W
Factor is the ratio of a gas volume (of CO
2
or O
2
) found in the combustion products to the heat content of the fuel.
SUMMARY OF THE INVENTION
The monitoring ofafossil-fired system may involve detailed and complete descriptive understanding of the fuel being burned, analyses of all major components, and accurate determination of its fuel flow. Such monitoring is possible by applying the Input/Loss Method discussed in '711 and '198. However, for many fossil-fired systems simpler methods are needed which allow the installation of analytical tools which provide an inexpensive, but consistent, indication of a system's thermal performance. From such indication, the system's efficiency may be monitored, deviations found, and corrections implemented. This invention discloses such atool. Its accuracy is not at the level of the Input/Loss Method, but has been found to be within 1% to 2% when monitoring on-line, and, as importantly, has been demonstrated to be consistent.
This invention employs both the L Factor and F Factor to determine system heat rate. Although the heat rate computed using the EPA's F Factor may not be as accurate as one determined from the L Factor, its accuracy still may be tolerable and useful given the ease in its computation. The L Factor and the F Factor may be used to determine heat rate only if certain correction factors are applied as taught by this invention. These correction factors are both conceptual and for routine measurement error.
The present invention, termed the F Factor Method, determines total fuel energy flow of a fossil-fired system resulting, when the total fuel energy flow is divided by the measured system electrical output, the heat rate of the system. Acceptable heat rate accuracy is achievable through the demonstrated high consistency found in a corrected L Factor based on the F Factor, to which this invention makes unique advantage.
The F Factor method does not use any part of the Heat Loss Method, it does not compute nor need any thermal loss term as used by Roughton. Unlike Roughton's method, the F Factor method employs the principle effluent flow or fuel flow associated with afossil-fired system.
This invention is unlike the works of Munukutla and Sarunac, et al, several key areas. First, as taught by this invention, system heat rate using the F Factor is directly proportional to the concentration of effluent CO
2
, not inversely proportional as stated by these authors. Further, this effluent CO
2
is associated with theoretical combustion, not actual combustion as these authors believe; but the actual value may be corrected to the theoretical. Further, it has occurred during the development of this invention that certain conceptual correction factors must be applied to the F Factor to correctly and accurately monitor a fossil-fired system. No corrections of any kind are mentioned by these authors. This is significant to this invention for the F Factor affords one method of computing the L Factor, however conceptual corrections which have been found to apply to the L Factor, also fundamentally apply to the F Factor. And lastly, these authors make no mention ofthe molecular weight, or alternatively the assumed composition, or alternatively the density of the total effluents being produced which this invention teaches must be addressed as different fossil fuels produce different mixes of combustion products comprising the total effluents.
In the process leading to the present invention, several problems existing with the F Factor concept have been both clarified and solutio
Barlow John
Exergetic Systems LLC
Sun Xiuqin
LandOfFree
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