Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Chemical analysis
Reexamination Certificate
2002-03-01
2004-03-30
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Chemical analysis
C700S274000
Reexamination Certificate
active
06714877
ABSTRACT:
This invention relates to a fossil-fired thermal system such as a power plant or steam generator, and, more particularly, to a method for determining correction factors to a set of “Choice Operating Parameters”, including effluent concentrations, such that combustion stoichiometric consistency and thermodynamic conservations of the system are both achieved. Correcting Choice Operating Parameters is accomplished through multidimensional minimization techniques operating on “System Effect Parameters” which are reflective of the system at large including system heat rate. The corrected Choice Operating Parameter may then be supplied to Input/Loss methods as used to determine fuel chemistry, heating value, fuel flow and other parameters for the monitoring and improvement of system heat rate.
BACKGROUND OF THE INVENTION
The importance of accurately determining system heat rate is critical to any thermal system (heat rate being inversely related to system thermal efficiency, common units of measure for heat rate are Btu/hour per kilowatt, or Btu/kWh). If practical hour-by-hour reductions in heat rate are to be made, and/or problems in thermally degraded equipment are to be found and corrected, then accuracy in determining system heat rate is a necessity. Accurate system heat rates using “Input/Loss methods” are achievable given input data with no discernable error. Specifically, “The Input/Loss Method” and its associated technologies are described in the following U.S. patent applications: Ser. No. 09/273,711 (hereinafter termed '711), Ser. No. 09/630,853 (hereinafter termed '853), Ser. No. 09/827,956 (hereinafter termed '956), and Ser. No. 09/971,527 (hereinafter termed '527); and in their related provisional patent applications and Continuation-In-Parts. Rudimentary Input/Loss methods are described in U.S. Pat. No. 5,367,470 issued Nov. 22, 1994 (hereinafter termed '470), and in U.S. Pat. No. 5,790,420 issued Aug. 4, 1998 (hereinafter termed '420). In addition to The Input/Loss Method as described in '711, the subject of the present invention relates to any method which uses measurements of effluent concentrations, typically CO
2
and O
2
, and other non-flow “Operating Parameters”, and when using this data determines one or more of the following: fuel flow, effluent flow, emission rates, fuel chemistry, fuel heating value, boiler efficiency, and/or system heat rate. Meanings of terms specific to this invention and delineated by quote marks are defined below.
Two highly sensitive inputs to Input/Loss methods are the CO
2
and H
2
O effluent concentrations as measured, or as otherwise determined, at the boundary of the system. There are other sensitive inputs such as effluent O
2
. The importance of accurately measuring effluent concentrations and Operating Parameters has been discussed by the present inventor in his U.S. patents and applications cited herein. His works have stressed the importance of such measurement accuracy, especially when monitoring a power plant in real-time, for making essentially continuous improvements. Such concern for measuring effluents in a direct manner, as required by '470 and '420, resulted in the invention of a high accuracy infrared instrument described in U.S. Pat. No. 5,327,356, whose technology was supported when applied to coal-fired systems by U.S. Pat. No. 5,306,209.
The invention of '470 is noteworthy as background for this invention for it teaches to repetitively adjust, or iterate, on “an assumed water concentration in the fuel until consistency is obtained between the measured CO
2
and H
2
O effluents and those determined by stoichiometrics based on the chemical concentration of the fuel”. Some aspects of '470 are dependent upon high accuracy directly measured CO
2
and H
2
O effluent concentrations. The difficulty is that high accuracy measurements may not be possible. Another difficulty with the details of '470 lies with the fact that adjusting fuel water as taught in '470, which alters the computed effluent water, has no prima facie effect on a dry-base effluent CO
2
. It is true, for example, that if fuel water is increased, the relative fraction of the other fuel's constituents, per mole of total As-Fired fuel, will decrease assuming that the fuel's other constituents, nitrogen, oxygen, carbon, hydrogen, sulfur and ash, remain proportionally constant to each other. However, it would be unusual that any given fuel water adjustment would produce an exactly consistent effluent CO
2
and O
2
; with the exception where the dry chemistry is constant. Further, if the fuel has a variable ash content, ash having a pure dilutive or concentrative influence on fuel chemistry and fuel heating value, then such a variable effect could not possibly be determined by merely iterating on fuel water. A higher assumed fuel water may decrease a wet-base effluent CO
2
, but the actual fuel could contain much lower ash, thus actually increasing the amount of fuel carbon relative to the whole. The approach of simple water iterations of the '470 patent is useful in certain situations, such as where the coal fuel bears little and constant ash, and, further, where high accuracy and consistent effluent CO
2
and H
2
O measurements are made. However, '470 has limitations given a lack of technology in assuring consistency in combustion stoichiometrics and for relying on high accuracy effluent measurements.
The invention of '420 extends the approach of '470 to include combustion turbine systems. The '420 patent is concerned with methods for improving heat rate, determining effluent flows and determining fuel flow of fossil-fired systems through an understanding of the total fuel energy flow (fuel flow rate times heating value). '420 explains that the molar quantity of fuel water “is iterated until convergence is achieved”; i.e., using direct, unaltered, effluent measurements resulting in an As-Fired heating value and fuel flow rate. Again, as water is altered, the aggregate of all other fuel constituents are altered in opposite fashion to maintain a normalized unity moles of fuel. As with the approach of '470, '420 requires high accuracy instrumentation, stating “the apparatus necessary for practicing the present invention includes utilization of any measurement device which may determine the effluent concentrations of H
2
O and CO
2
to high accuracy”. When considering direct effluent measurements required for Input/Loss methods, such as effluent concentrations of CO
2
, O
2
, and other Operating Parameters, measurement errors rarely cancel and no single instrument has perfect accuracy.
The problem which is not addressed by '470 or '420 Input/Loss methods is that great sensitivity may exist between an effluent concentration measurement and a parameter which effects system heat rate. This is best illustrated by the sensitivity effluent CO
2
has on a computed heating value: a 1.0% &Dgr;molar/molar change in CO
2
will produce a 2.7% change in heating value for a typical Powder River Basin coal. This typically implies 270 &Dgr;Btu/kWh in heat rate, which may be worth at least $5 million/year in fuel costs for a 600 Mwe coal-fired system. Further, it is the nature of power plant stoichiometrics that essentially any selection of Choice Operating Parameters have inter-dependencies. A 1.0% change in CO
2
may be easily caused by non-fuel induced changes within the system: in air pre-heater leakage; in Forced Draft Fan bias effecting combustion air flow; in burner configurations; in fuel water content; and so forth. A method is needed in which such inter-dependencies are considered.
Complete thermodynamic understanding of fossil-fired thermal systems, for the purposes of improving heat rate and accuracy in regulatory reporting of data, requires the determination of fuel flow rate, fuel chemistry, fuel heating value, boiler efficiency, total effluent flow, emission rates of the common pollutants, and system heat rate. When determining these quant
Barlow John
Exergetic Systems LLC
Taylor Victor J.
LandOfFree
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