This invention relates to any fossil fueled thermal system, and especially relates to large commercial steam generators used in power plants, and, more particularly, to a method and apparatus for determining fuel chemistry in essentially real time based on effluents resulting from combustion, associated stoichiometrics, and the genetics of the fossil fuel. Knowing the system's fuel chemistry, the fuel calorific value, the fuel flow and the thermal performance associated with the thermal system may then be determined in essentially real time.
Although especially applicable to “The Input/Loss Method” as installed at fossil-fired power plants, this invention may also be applied to any one of the “Input/Loss methods” installed at any thermal system burning a fossil fuel. Definitions for quoted terms are provided in the section entitled MEANING OF TERMS. The following paragraphs discuss prior art associated with The Input/Loss Method and with generic Input/Loss methods.
The principle background teachings of The Input/Loss Method are described in three patents: U.S. Pat. No. 6,584,429 which issued Jun. 24, 2003 and teaches a high accuracy method of determining boiler efficiency, hereinafter referred to as '429; U.S. Pat. No. 6,714,877 which issued Mar. 30, 2004 and teaches how effluent concentrations resultant from combustion may be corrected for errors, hereinafter referred to as '877; and, most importantly, U.S. Pat. No. 6,522,994 which issued Feb. 18, 2003 and teaches general methods of The Input/Loss Method. U.S. Pat. No. 6,522,994 originated as a PCT application resulting in the following patents: Canadian Patent 2325929; Australian Patent 762836; and European Patent (DE, GB, GR & IT) 1171834. These patents, U.S. Pat. No. 6,522,994, Canadian 2325929, Australian 762836 and European 1171834, are hereinafter collectively referred to as '994.
'994 is incorporated herein by reference in its entirety. '429 is incorporated herein by reference in its entirety. '877 is incorporated herein by reference in its entirety. In addition to '994, '429 and '877, a considerable technological foundation for The Input/Loss Method may be found in the following U.S. Pat. Nos. 6,560,563, 6,651,035, 6,691,054, 6,745,152, 6,799,146, 6,810,358, 6,868,368 and 6,873,933.
Further still, related pending applications which again add to the technology of The Input/Loss Method include the following: Canadian Patent Application No. 2479238, European Patent Office Application No. 02784559, and U.S. patent application Ser. No. 10/715,319. Canadian Patent Application No. 2479238 and European Patent Office Application No. 02784559 are the same, stemming from PCT/US02/37612 (WO2003/091881). The originating U.S. application represented by PCT/US02/37612 resulted in U.S. Pat. No. 6,651,035 which teaches how tube failures in large steam generators may be detected using The Input/Loss Method. U.S. Pat. No. 6,651,035 was originally filed as a U.S. Continuation-In-Part to an application which became U.S. Pat. No. 6,745,152. U.S. patent application Ser. No. 10/715,319 has resulted in an allowed U.S. application which principally teaches how tube failures in Recovery Boilers may be detected using The Input/Loss Method modified for sodium/hydrocarbon stoichiometrics, that application was published as US2004/128111.
One of the Input/Loss methods, a rudimentary method, is described in U.S. Pat. No. 5,367,470 which issued Nov. 22, 1994 (with Dec. 14, 1989 priority), and in U.S. Pat. No. 5,790,420 which issued Aug. 4, 1998. U.S. Pat. No. 5,790,420 was originally filed as a U.S. Continuation-In-Part to an application which became U.S. Pat. No. 5,367,470.
Other known Input/Loss methods are thoroughly discussed in the BACKGROUND OF THE INVENTION section of '994; this discussion is referenced herein as being important.
For many years the energy industry has attempted to categorize coals. Although there are four major ranks of coal in the U.S. classification scheme (anthracite, bituminous, sub-bituminous and lignite), these have been sub-divided by ASTM D388, “Standard Classification of Coals by Rank”. Refer to TABLE B1 for ASTM D388 categories (an incorrect energy conversion was used in this standard, 2.3255 kJ/kg/Btu/lb, versus 2.3260 kJ/kg/Btu/lb). One problem immediately seen in TABLE B1 is its lack of specificity, ASTM D388 basically employs either As-Received calorific values, and/or proximate analyses on a dry basis to judge coals. “Ultimate Analysis” data is not employed. Higher Rank coals are classified according to fixed carbon on a dry basis while the lower Rank coals are classified by As-Received calorific value (wet basis). Figure X1.1 of ASTM D388 presents a typical single-variant correction between weight fraction of volatile matter and Reflectance in oil. A general discussion of coal classifications may be found in the text The Chemistry and Technology of Coal by J. G. Speight, Marcel Dekker, Inc, New York & Base1, which discusses coal classifications in Chapter 1 (pages 3-19), elemental analysis on pages 83-84 and evaluation techniques in Chapter 8 (pages 165-199). Note that examples of single-variant analyses are presented in this text's FIG. 1.2, FIG. 8.10 and FIG. 8.12 and FIG. 8.11; several of these displaying weight fraction of fuel hydrogen versus weight fraction of fuel carbon. As seen, these plots represent only broad-brush correlations, hardly capable of supporting of any of the Input/Loss methods.
There are seemingly as many coal categories used in Europe as countries. In general, Europeans categorize coal as either hard or soft depending on ash-free calorific value. Sub-groups are then classed by volatile matter, coking properties, etc. resulting in a complex three-digit numbering system. No European system employs Ultimate Analysis data to classify coals, at best proximate analyses are employed. Refer to “Brown Coals and Lignites—Classification by Types on the Basis of Total Moisture Content and Tar Yield”, International Organization for Standards, ISO 2950-1974(E).
It is also useful to recognize that the analysis of fossil fuels may be accomplished using the Excel® computer program. Excel is owned by the Microsoft Corporation, Redmond, Wash. state in the U.S. Excel is a registered trademark of Microsoft Corporation. Fossil fuel data is typically obtained as Ultimate Analysis data with As-Received fuel water, fuel ash and calorific values. As used to develop this invention, and used throughout its presentation herein, such data was analyzed using Excel. All “R2 values” mentioned herein, commonly termed the Coefficient of Determination, have been computed by Excel using regression analysis. Excel's R2 value represents the percent variation in a y-variable that is explained by the independent x-variable. Only linear regression was used herein. There are classical problems associated with R2 values as are well known to one skilled in statistics. One such problem, and one important to this invention, is evident when data presents an even scatter about a linear mean. Such a situation might lead to a high R2 value which does not truly reflect a y-variable being predictable by the independent x-variable (simply put, the R2 value may appear acceptable, but the functionality is too coarse to be useable). The most straightforward method to address such situations is to simulate data patterns associated with their end use and to then evaluate the direct impact their variances have on computed output. For example, the impact on The Input/Loss Method's computed calorific value of a 1.0% variance in predicted fuel carbon (and thus affecting computed calorific value) may be assessed most conservatively by assuming a 1.0% variance in effluent CO2; such a 1.0% variance may be observed, and verified, from plotted data. Another method of evaluating distributed data patterns is to simply apply engineering judgement by looking at the plots: they are either unreasonable or portent fundamental understanding with obvious certainty.
The technologies underwriting The Input/Loss Method, witnessed by the aforementioned patents and patent applications, were based on recognizing that if the effluent concentrations from combustion are used to determine fuel chemistry, then fundamentally more unknowns are involved than practical equations are available. '994 presented a solution to this problem by teaching that fuel hydrogen may have a functional relationship with fuel carbon; see Eq. (45) in '994 and the definition of “reference fuel characteristics” in '994. Other relationships are fuel oxygen versus fuel carbon, and fuel nitrogen versus fuel carbon; refer to Eqs. (43) and (44) in '994 and associated discussion above Eq. (42) in '994. For example, the correlation constants A5 & B5 used in Eq. (45) in '994 derive directly from the data, for example, as seen in FIG. 3 of '994. Eq. (42) in '994 presents an explicit solution to moisture-ash-free (MAF) molar fuel carbon employing correlation coefficients: A3 & B3 from MAF molar fuel oxygen as a function of MAF molar fuel carbon of Eq. (43) in '994; and A5 & B5 from MAF molar fuel hydrogen as a function of MAF molar fuel carbon of Eq. (44) in '994. These correlations provided the missing equations. They all are simple single-variant molar correlations using hydrogen versus carbon, or oxygen versus carbon; e.g., the single-variant is molar hydrogen as observed in '994 Eqs. (45). There was no other known art or techniques for solving the underlying problem.
Wherein The Input/Loss Method has been installed at a number of power plants, certain situations have arisen in which single-variant relationships such as fuel hydrogen versus fuel carbon are simply not adequate. This has been found true when employing “reference fuel characteristics” as defined and taught in '994. It has been found that this situation is especially true if dealing with the following fuel types: Irish peat; Powder River Basin coals; and what is termed “High Seas” coal. Irish peat is of importance as it represents a typical indigenous fuel source, not only for the Republic of Ireland, but also for Poland, for Finland and for Minnesota in the U.S. Peat's dry chemistry may vary considerably given its haphazard formation as immature coal, and its fuel water content typically varies wildly. The MAF characteristics of peat are not unlike lignite found in Texas, Australia and Greece. Powder River Basin coals have an enormous, and growing, financial impact on the United States and Canada as it represents the largest single source of coal fuel being fired in North American power plants. Over 120 power plants use Powder River Basin coals, growing by some estimates at 15%/year. Powder River Basin coals have low sulfur concentrations, but are high in fuel water with highly variable fuel chemistries reflecting over a dozen mines located in several western states in the U.S. High Seas coal is defined as high energy coal which is frequently bought, literally, while coal-carrying cargo ships are on the high seas. It may be categorized, as high volatile bituminous coal. High Seas coal typically has low fuel water, but fuel chemistries reflecting variability associated with world-wide sourcing. High Seas coal typically has calorific values in the range of 25,586 to 31,401 kJ/kg (11,000 to 14,000 Btu/lbm). There are other fuels which, it is anticipated, will receive higher interest over the coming years, but which will have similar variabilities. One such fuel is switch grass, grown in the U.S. as an environmentally friendly (and renewable) fossil fuel. Another, is wood waste (i.e., bio-mass fuel), being burned in the western states of the U.S. If Irish peat, Powder River Basin coals and High Seas coals were not significantly used, then the method taught in '994 would be adequate given a supposed well-characterized fuel. By well-characterized is meant that needed correlations (e.g., MAF molar fuel hydrogen as a function of MAF molar fuel carbon) have R2 values which exceed 90%. Note however that if an R2 value at 90% is considered inadequate (versus, say 98%), or not, the practical application of '994 was, indeed, limited to this level of predictability as a direct consequence of simple single-variant correlations.
It is important to note that “reference fuel characteristics”, as defined in '994, represents a taught procedure, one in which hydrogen versus carbon relationships are developed based on historical fuel data. It does not specify usable data. When the method of '994 was installed in PRB burning powers plants, coal from specific regions within the Basin would require characterization. The Boardman Coal Plant, operated by Portland General Electric and using The Input/Loss Method, was characterized specifically to PRB Decker coal. The Nebraska City Unit 1, operated by Omaha Public Power District and using The Input/Loss Method, was characterized specifically to PRB Caballo Rojo coal. And the same even for Irish peat. The Lough Ree Power Station, operated by the Electricity Supply Board and using The Input/Loss Method, was characterized specifically to Irish peat found near Lanesboro, Ireland, although the West Offlay Power Station, also burning Irish peat, not 56 km (35 miles) away, was characterized specifically to the Shannonbridge region. '994 taught a procedure requiring historical data, requiring unique reference fuel characteristics to be programmed in a computer for each installation. What is needed is a generic method such that a single procedure satisfies an entire Rank of coal, without routine need of historical data. At the time of '994 there was no other known art. When considering variable fuels, as defined by poor R2 values resultant from using simple single-variant correlations, the '994 method has not proven to be generic as it suffers from a lack of flexibility under certain circumstances.
The databases of Ultimate Analyses and calorific values used to develop this invention derive from the following sources: 1) Pennsylvania State University, Organic Petrology Laboratory database containing over 1200 Ultimate Analyses and associated calorific values from over 400 mines; 2) Powder River Basin coal data containing approximately 250 samples from 19 different regions within the Basin; 3) so-called High Seas coal data containing 320 samples from over 50 mines from 14 states in the U.S., South Africa, Poland, Russia and Colombia, this data includes numerous spot analyses obtained from power plants actually using such coal (i.e., from the Moneypoint station, Republic of Ireland, from the Brandon Shores station, Maryland state in the U.S., and from the Jorf Lasfar station, Morocco); and 4) Irish peat data containing approximately 160 samples from 6 different regions within the Republic of Ireland, notably the data having been collected over a considerable time period, from 1963 through 2005. In total the analyzed data consisted of approximately 1930 Ultimate Analyses and corresponding calorific values.
As seen in
As demonstrated in
This invention relates to any fossil fueled thermal system, and especially relates to large commercial steam generators used in power plants, and, more particularly, to a method and apparatus for determining fuel chemistry in essentially real time based on effluents resulting from combustion, associated stoichiometrics, and the genetics of the fossil fuel based on multi-variant analysis. In addition, this invention teaches a device which evaluates Ultimate Analysis data providing diagnostic information on the sample of coal. The use of “multi-variant analysis” has lead to the discovery of the “genetics of fossil fuels”, numerically defining a wide range of fossil fuels. Further extension of the multi-variant analysis technique has lead to a new L-Factor, termed L10, which may be used to correct effluent concentrations and other “Choice Operating Parameters” using '877 methods. Knowing the system's fuel chemistry, the fuel calorific value, the fuel flow and the thermal performance associated with the thermal system may then be determined in essentially real time. The teachings of this invention may be implemented for monitoring any thermal system burning a fossil fuel, or a thermal system burning a mix of fossil fuels and inorganic fuels such as Recovery Boilers. Such monitoring is assumed to be conducted in a continuous manner (i.e., on-line, in essentially real time), processing one monitoring cycle after another.
This invention, through new a method, apparatus and device, extends the technology associated with Input/Loss methods and teaches its industrial use by computer producing a complete As-Fired fuel chemistry and to evaluate Ultimate Analysis data. Specifically The Input/Loss Method has been applied through computer software, installable on a personal computer termed a “Calculational Engine”, and has been demonstrated as being highly useful to the operators of fossil-fired systems. The Calculational Engine receives data from the system's data acquisition device. The Calculational Engine's software consists of the ERR-CALC, EX-FOSS, FUEL and HEATRATE executable computer programs described herein, and in '994, '429 and '877. The programs ERR-CALC and HEATRATE having been modified by the teachings of this invention. The Calculational Engine continuously monitors system efficiency on-line, i.e., in essentially real time, as long as the thermal system is burning fuel. The application of this invention to The Input/Loss Method significantly enhances the system operator's ability to understand coal-fired power plants.
The present invention provides a procedure, termed multi-variant analysis, which allows discovery of the genetics of fossil fuels, from which generates matrix solution to fuel chemistry based on effluents (“Choice Operating Parameters”).
The present invention provides a new L-Factor, termed L10, which allows effluents from combustion to be corrected using the methods taught in '877. The high consistency observed in L10 has resulted directly from the genetics of the fossil fuel as based on multi-variant analysis.
The present invention, founded on multi-variant analysis, also teaches how fuel flow may be computed, and with a determined boiler efficiency and knowing the energy flow to the working fluid, results in a system thermal efficiency through which the system operator receives essentially real time feed-back as to whether his/her adjustments to the system do good or harm to efficiency.
The present invention teaches a new method to classify coals, replacing or improving common standards such as ASTM D388 and ISO 2950. The present invention also provides a method and device to distinguish data outliers associated with Ultimate Analyses.
Other objects and advantages of the present invention will become apparent when its general methods are considered in conjunction with the accompanying drawings and the related inventions of '994, '429 and '877.
According to a first embodiment the present invention provides a method for quantifying the operation of a thermal system burning a fossil fuel having a heat exchanger/combustion region producing combustion products, the method comprising the steps of:
before on-line operation,
while operating on-line,
the step of operating on-line comprising the steps of
According to a second embodiment the present invention provides a method for quantifying the operation of a thermal system burning a fossil fuel having a heat exchanger/combustion region producing combustion products, the method comprising the steps of:
before on-line operation,
while operating on-line,
the step of operating on-line comprising the steps of
One of the advantages of these method embodiments is that they allow the genetics of fossil fuels to be determined based on multi-variant analysis. As will be apparent from the following description, each fossil fuel has unique molecular characteristics which are now knowable. Thus, as has been found when developing this invention, multi-variant relationships differ between broad fuel types, and differ consistently. A further advantage of the methodologies of the present invention is that they allow elucidation of the genetics of fossil fuels such that a reliable set of independent equations, including stoichiometric equations independent of correlation constants, can be formed to resolve a complete As-Fired fuel chemistry based on effluent concentrations by matrix solution.
According to a third embodiment the present invention provides for an apparatus for assisting the operation of a thermal system burning fossil fuel, the apparatus comprising:
a data acquisition device to collect data from the thermal system including at least a selection of Choice Operating Parameters, the data acquisition device producing a set of acquired system data;
a computer with a processing means;
a set of instructions for configuring the processing means to determine a fuel chemistry of the fossil fuel and to receive as input the set of acquired system data, resulting in a programmed computer;
means by which the programmed computer receives as input the set of acquired system data;
the programmed computer producing the fuel chemistry of the fossil fuel; and
means for reporting the fuel chemistry of the fossil fuel to assist in the operation of the thermal system.
According to a forth embodiment the present invention provides a device for evaluating an Ultimate Analysis of a coal sample, the device comprising:
a set of instruments capable of producing the Ultimate Analysis of a coal sample and to produce an Ultimate Analysis output, said output comprising at least carbon, hydrogen and oxygen concentrations;
a data processing device with a processing means and a memory means wherein the memory means stores a set of descriptive fossil fuel data based on the genetics of fossil fuels organized by categories;
a set of instructions for configuring the processing means to compare the Ultimate Analysis with the set of descriptive fossil fuel data and to receive as input the Ultimate Analysis output from the set of instruments, resulting in a programmed data processing device capable of producing a comparative report on the Ultimate Analysis;
the set of instruments producing the Ultimate Analysis output;
means of communicating the Ultimate Analysis output from the set of instruments to the programmed data processing device;
the data processing device producing the comparative report on the Ultimate Analysis; and
means of communicating the comparative report on the Ultimate Analysis.
One of the advantages of the apparatus embodiment of this invention is that it provides a computing vehicle for calculating a real time complete As-Fired fuel chemistry of a coal-fired power plant, providing needed information to the operator. Also, one of the advantages of the device embodiment of this invention is that it provides a computing vehicle for evaluating Ultimate Analysis data, providing diagnostic information on coal sample analyses. Both of these advantages stem from the consistency found in the genetics of fossil fuels.
To assure an appropriate teaching of this invention, its description is divided by sub-sections. The first two present nomenclature, definitions of equation terms, typical units of measure, and meaning of terms used herein (such as Choice Operating Parameters and System Effect Parameters, the genetics of the fossil fuel, etc.). The remaining sub-sections, representing the bulk of the teachings, are divided as follows: system stoichiometrics; genetics of fossil fuels; the L10 Factor and its use; determining complete As-Fired fuel chemistry; determining calorific value, boiler efficiency, fuel and effluent flows; correcting Choice Operating Parameters which includes a discussion on benchmarking real time monitoring systems; and the Calculational Engine apparatus required to operate this invention. These principle sections are then followed by a conclusion, THE DRAWINGS and related teachings. Determining a high accuracy boiler efficiency is taught in '429. Teachings of multidimensional minimization techniques, as applicable to this invention are presented in '877. The present invention expands the accuracy and consistency of all Input/Loss methods when monitoring fossil fired steam generators in real time, and specifically builds upon and expands the utility of The Input/Loss Method described herein and in '994, '429 and '877.
Definitions of Equation Terms and Typical Units of Measure
Stoichiometric Terms:
JAct=Total effluent water at the system's boundary (j+ bAβ); moles/base.
Quantities Related to System Terms:
HAct=Relative humidity of ambient air local to the thermal system as a function of the psychrometric state; see Operating Parameters; fraction.
Subscripts and Abbreviations:
The words “Operating Parameters”, as taken within the general scope and spirit of the present invention, mean common data obtained from a thermal system applicable to the thermodynamic understanding of that system. The following quantities may be included in the definition of Operating Parameters, they are not encompassing but considered typical of a minimum set of data required for such thermodynamic understanding: effluents CO2 and O2 concentrations determined at the Stack, or before the air pre-heater (Boiler side of the air pre-heater); effluent SO2 concentration if fuel sulfur is present, determined at the Stack, or before the air pre-heater (Boiler side of the air pre-heater); the mass, wet-base ratio of the indicated combustion air flow at the system's combustors, to the indicated plant fuel flow, termed AFAct (note that AFAct is obtained only for the determination of fuel ash as taught herein); effluent H2O concentration measurement, or assumptions made (or as otherwise may be determined); effluent temperature measurement, that is the average temperature associated with the combustion gases at the system boundary (caution must be exercised in measuring non-stratified gas flows); the inlet/outlet ratio of CO2 (producing RAct as is preferred), or O2 (producing R′Act) across the air pre-heater where these ratios could be obtained on-line, off-line, based on periodic testing or judgement of such ratios used for the determination of air pre-heater leakage; determination of fuel temperature at an appropriate system boundary; air psychrometric measurements leading to relative and specific humidities, or as otherwise determined, at the system boundary (e.g., dry and wet bulb temperatures, or dry bulb and relative humidity, or dry bulb and dew point temperatures); quantities comprising the system's Firing Correction term, HBC as taught in '429; the discharge temperatures of the air as it exits each air heating or cooling device but before it reacts with the fuel (for example, such devices might include the air pre-heater, forced-draft fan, steam-to-air heater, etc.); and similar quantities. Operating Parameters also include a basic understanding of the fuel being burned: its general classification, its general water and its ash contents, and typical calorific values to be expected. Operating Parameters include the energy flow to the working fluid heated by combustion products (BBTC). For a typical steam generator, the measurements required to determine BBTC typically include feedwater flow to the steam generator, feedwater pressure and temperature, determination of the steam flow from the steam generator if different than the feedwater flow, steam pressure, steam temperature or quality (or assumed quality), and, if applicable, reheat flows, and reheat inlet and outlet pressures and temperatures. If employing a Reheater heat exchanger, determination of accurate reheat flows generally requires understanding of steam turbine flow distributions (involving high pressure turbine shaft seals, steam flows to feedwater heaters, turbine bypass leakages, attemperation spray flows and the like). Operating Parameters also include the electrical generation produced (Woutput) if the working fluid powers a turbine-generator cycle.
The words “Choice Operating Parameters” (COP), as taken within the general scope and spirit of the present invention, are defined as meaning any sub-set of Operating Parameters which directly impact system stoichiometrics, and thus may impact the determination of fuel chemistry as taught herein. This invention assumes that Choice Operating Parameters may have error, said error may adversely affect the determination of fuel chemistry, but said error may be corrected as taught herein and through the optimization methods of '877. In the Preferred Embodiment Choice Operating Parameters are selected by the user of this invention from an available set. This available set of Choice Operating Parameters includes the following nine: 1) effluent CO2 concentration measured at the Stack or Boiler; 2) H2O concentration measured, or as otherwise may be determined, at the Stack or Boiler; 3) the mass, wet-base ratio of the indicated combustion air flow at the system's combustors, to the indicated plant fuel flow, the Air/Fuel ratio termed AFAct; 4) the Air Pre-Heater Leakage Factor, termed RAct, which may be ≧1.00, where unity (=1.00) indicates no leakage is present (as may be the case with Tubular Air Heaters); 5) the concentration of O2 in the combustion air local to the system, or as otherwise determined, termed AAct (leading to the determination of φAct); 6) the system's indicated plant limestone flow, termed mLS; 7) effluent O2 concentration measured at the Stack or Boiler; 8) mass flow associated with a heat exchanger tube leakage, termed mT; and 9) the relative humidity of the ambient air local to the thermal system and which is associated with its combustion air, termed HAct.
The words “System Effect Parameters” (SEP), as taken within the general scope and spirit of the present invention, mean any parameter of the thermal system or its fuel which directly impacts the determination of system efficiency. In the most general sense System Effect Parameters include any parameter used in Eqs. (103), (104A) through (107B) which compute system efficiency and thus system heat rate. For the Preferred Embodiment, System Effect Parameters include the following four types of quantities: the L10 Factor; the computed As-Fired fuel flow (mAF); the gross calorific value (either HHVAF, HHVDRY or HHVMAF); and the As-Fired fuel water fraction (WFH2O) which may be used for determination of tube leakage or to convert HHVDRY to HHVAF. The computed L10 Factor affects fuel chemistry which affects calorific value and boiler efficiency, and thus has an immediate impact on system efficiency. “Reference System Effect Parameters” are constant and targeted (i.e., desired) System Effect Parameters to which the System Effect Parameters are numerically driven by the minimization techniques through optimizing a selection of Choice Operating Parameters.
The words “Input/Loss methods”, as taken within the general scope and spirit of the present invention, mean any method or combination of methods in which one or more of the following parameters is determined based on effluent concentrations and/or a selection of Choice Operating Parameters: moisture-ash-free fuel chemistry, dry fuel chemistry (i.e., water free), complete As-Fired fuel chemistry, fuel calorific value (i.e., fuel heating value), boiler efficiency, fuel flow, and/or effluent flow. In addition to '994, '429 and '879 and related patents, Input/Loss methods include the methods of U.S. Pat. Nos. 5,367,470 and 5,790,420. The words “The Input/Loss Method” refers specifically to the collection of technologies described in '994, '429 and '879, in addition to the teachings disclosed herein.
As used herein, the words “Calculational Engine” refers to a computer with a processing means and a memory means. Typically said computer is a common personal computer in which software descriptive of The Input/Loss Method as taught herein is installed (i.e., resulting in a programmed computer). Said computer may also include, broadly, any data processing unit such as a specialized computer, a hand-held computer, or an integrated circuit, all of which are capable of receiving sets of instructions and has memory (i.e., having a processing means and a memory means).
As used herein, if used, the words “obtain”, “obtained”, “obtaining”, “determine”, “determined”, “determining”, “determination”, “establish”, “established” or “establishihg” are defined as measuring, calculating, computing, assuming, estimating or gathering from a database.
As used herein, the words “monitoring” or “monitored” are meant to encompass both on-line monitoring (i.e., processing system data in essentially real time) and off-line monitoring (i.e., computations involving static data). A “monitoring cycle” is meant to be one execution of the processes described in
As used herein, the words “smoke Stack” or “Stack” or “system boundary” are defined as the physical boundary of the thermal system where gaseous combustion effluents exit, entering the local environment; refer to 43 in
As used herein, the words “Boiler” or “Boiler Effluent” are defined as the region 35 in
As used herein, the words “Fuel Iterations” are defined in conjunction with a detailed description of
As used herein, the word “indicated” when used in the context of data originating from the thermal system is defined as the system's actual and uncorrected measurements of a physical process (e.g., pressure, temperature, mass flow, volumetric flow, density, and the like) whose accuracy or inaccuracy is not assumed. As examples, a system's “indicated plant fuel flow” or its “indicated plant limestone flow” denote system measurements the accuracy of which is unknown (they are “as-is”, with no judgement applied). Such indicated measurements are said to be either correctable or not. If not correctable, it may be that the associated computed value from Input/Loss methods tracks the indicated value over time (the indicated not being corrected per se). In the case of indicated plant limestone flow when used as a Choice Operating Parameter (Λ6), it is directly corrected as taught by this invention. In the case of indicated plant fuel flow when used as a System Effect Parameter, it may be shown that the computed fuel flow, mAF, tracks the indicated plant fuel flow, mAF-pLT.
As used herein, the words “genetics of fossil fuels” or “genetics of the fossil fuel” are defined as the specific chemical patterns found common to certain fossil fuels as based on “multi-variant analysis”. Genetics of fossil fuels results in elemental patterns numerically descriptive of molar relationships, for example the CHc2Oc3 relationships as taught through TABLE 6. As defined, the term derives from the word “genesis” taken, in the context of this invention, as meaning to understand the chemical formation of fossil fuels. Multi-variant analysis consists of a combination of two or more elemental fuel constituents, multiplied by the same quantity, related mathematically to another elemental fuel constituent. The combination of two or more elemental fuel constituents may be dependent or independent quantities. Multi-variant analysis used herein comprise the following: combined MAF molar fuel carbon plus MAF molar fuel hydrogen as a function of MAF molar fuel oxygen; combined MAF molar fuel carbon plus MAF molar fuel oxygen as a function of MAF molar fuel hydrogen; or combined MAF molar fuel hydrogen plus MAF molar fuel oxygen as a function of MAF molar fuel carbon. Examples are found in Eqs. (61), (62), (63) and (72), and when Eq. (71) is combined with Eq. (72) eliminating L10. Note that these relationships and Eqs. (61), (62) and (63) employ diatomic hydrogen and diatomic oxygen, consistent with Eq. (29F), which is the Preferred Embodiment. Although the early discovery work anticipated specifying a molecular pattern using monatomic hydrogen and monatomic oxygen, both the monatomic and diatomic analyses produced essentially the same high Coefficients of Determination (if consistency developed). The diatomic is the Preferred Embodiment only since it is consistent with the combustion equation, Eq. (29F), thus eliminating conversion between different MAF bases. Also, there are other multi-variant analysis types which may be considered such as: combined MAF molar fuel carbon plus MAF molar fuel hydrogen plus MAF molar fuel sulfur as a function of MAF molar fuel oxygen; MAF molar fuel carbon less MAF molar fuel hydrogen as a function of MAF molar fuel oxygen; and so forth.
As used herein, the meaning of the words “using a genetics of the fossil fuel based on multi-variant analysis” is defined as using the information gathered from Eqs. (61), (62), (63), and (71) combined with (72), particular to a collection of fossil fuels of interest. Said information may be used to form one or more required equations used by a matrix solution to resolve fuel chemistry. Said data, and useable data, is found in TABLE 2, TABLE 3, TABLE 4, TABLE 7 and TABLE 8. This definition does not mean that all equations must be employed. For example, Eq. (72) after combining with Eq. (71) to form a re-ordered Eq. (74), is applied using the data found in TABLE 7 and TABLE 8; becoming equation #1 in the 5×5 matrix solution. See the section entitled DETERMINING THE COMPLETE AS-FIRED FUEL CHEMISTRY. Eq. (63) is applied using the data found in TABLE 4, re-ordered as Eq. (64); becoming equation #2 in the 5×5 matrix solution. In the 5×5 matrix solution there is no other information extracted from Eqs. (61), (62), (63), (71) or (72) which is required. The meaning of the words “developing a genetics of the fossil fuel based on multi-variant analysis” is defined as creating multi-variant relationships based on the general teachings of this invention, taken in the broadest interpretation of the inventive features discussed in this paragraph and elsewhere herein. For example, these teachings are not limited to multi-variant analysis involving only two elements; more than two may apply as would be applicable to equations of the form found in Eqs. (61), (62), (63) and (72).
As used herein, the meaning of the words “complete As-Fired fuel chemistry” is defined as comprising the following constituents of a fossil fuel: elemental carbon, elemental hydrogen, elemental oxygen, elemental sulfur, elemental nitrogen, mineral matter (ash), and water. It is understood by one skilled in the art that elemental hydrogen and elemental oxygen derive from the dry chemical make-up of the fossil fuel (water free) and are not influenced by the fuel's water content Often fuel water is termed “fuel moisture”; they mean the same. Fuel mineral matter is also termed “fuel ash”; they mean the same. Correctly stated, fuel ash is residue remaining after the combustion of a fossil fuel, commonly assumed to be the non-combustible mineral matter associated with the un-combusted fuel. The term “fuel ash” is commonly used in the industry, meaning mineral matter, and is employed herein. As used herein the terms “Ultimate Analysis” or “Ultimate Analyses” meaning multiple Ultimate Analysis, is defined as comprising the following constituents of a fossil fuel: elemental carbon, elemental hydrogen, elemental oxygen, elemental sulfur and elemental nitrogen. As strictly defined, an Ultimate Analysis is free of fuel gaseous components, free of fuel ash and free of fuel water; it truly represents Moisture-Ash-Gas-Free (MAGF) elemental constituents. For this disclosure, fuel gaseous components are not considered, they are considered however in '994, whose teachings of these terms, and other minor components of a fossil fuel, may be incorporated herein for expansion of the disclosure's methods by following the teachings found in '994. Note that an “As-Fired” condition refers to the actual fuel, with mineral matter and wet with water, in the state of being fired into the thermal system; that is, fuel 22 crossing the thermodynamic boundary 44 in
As used herein, the words “operating a programmed computer” or “operating the programmed computer” are defined as the action encompassing either to directly operate a programmed computer, to cause the operation of a programmed computer, or to authorize the operation of a programmed computer at a facility controlled by the authorizer. In like manner, the word “calculating”, for example in the context of “calculating a fuel calorific value” is defined as encompassing either to engage directly in the action of calculating, or to cause a calculating process through a programmed computer, or to authorize calculating process through a programmed computer at a facility controlled by the authorizer.
As used herein, the words “calorific value” and “heating value” mean the same. As used herein, the words “gross calorific value” and “higher heating value” mean the same. As used herein, the words “net calorific value” and “lower heating value” mean the same.
As used herein, the words “R2 value” or “R2 values” mean the Coefficient of Determination as computed by the Excel computer program using linear regression.
As used herein, the meaning of the word “quantifying” in the context of “quantifying the operation of a thermal system” is taken in the usual dictionary sense, meaning “to determine or express the quantity of . . . ”; for example, at a minimum what is being “quantified” is a complete As-Fired fuel chemistry.
System Stoichiometrics
Any study of the combustion of fossil fuels necessitates the formulation and use of a combustion equation. Combustion equations used by several Input/Loss methods are described in '994 by its designated Eq. (29), in '429 by its Eq. (19), in '877 by its Eq. (19-corr), in US2004/128111 by its Eq. (19BL). These combustion equations are cited to demonstrate the flexibility of the present invention to different situations. As examples: consideration of CaO as an ash constituent (termed αCaCO3), deriving from limestone found in the originating mineral matter is taught in '877 by its Eq. (19-corr); the study of black liquor fuel consisting of hydrocarbons and sodium compounds is taught in US2004/128111; and other variations are taught in the cited patents supporting The Input/Loss Method. This invention's methods are taught through a combustion equation defined by Eq. (29F) herein. Through Eq. (29F) stoichiometric terms become self-defined. Eq. (29F)'s nomenclature is unique in that brackets are used for clarity: for example, the expression “xα2[H2O]” means the moles of fuel water/base, algebraically simply xα1; the expression “dAct[CO2]” means the effluent moles of carbon dioxide/base, algebraically simply dAct; “βbA[H2O]” means the effluent moles of moisture found in the leakage air; etc. The stoichiometric base of Eq. (29F) is 100 moles of dry Stack gas (i.e., at the thermodynamic boundary).
Resolution of Eq. (29F) is had when all ni and nii quantities have been determined. Minor component terms of Eq. (29F) are typically resolved either through direct measurement (e.g., for CO and NO), or assume zero values, or through obtained relationships. All minor components typically have only low parts-per-million concentrations and thus have little impact. Although non-traditional fuel components such as α0[CYRHZR], α7[CO2], α8[CO] and α9[H2S] are not presented in Eq. (29F); treatment of such components is taught in '994 and whose teachings of these terms may be directly transferred. Note that the term α0[CYRHZR] represents a composite gaseous fuel which may be used for flame stability, as sometimes employed when firing with coal. As defined herein the principle unknown fuel constituents, resolved by this invention, include those indicated in Eq. (29F) as: α1[N2], α2[H2O], α3[O2], α4[α], α5[H2], α6[S] and α10[ash]. The minor effluents, eAct[CO], f[H2], l[SO3], m[NO], p[N2O], q[NO2], t[CYP1HZP1] and u[CYP2HZP2] are presented for generalized teaching; their values are assumed to be constant or otherwise obtained. More specifically, many times effluent CO is measured, NOx is measured generically then divided into NO, N2O and NO2 compounds based on estimation or periodic measurements. The unburned hydrocarbons CYP1HZP1 and CYP2HZP2 represent compounds which could be measured with hydrocarbon (combustibles) instrumentation, or otherwise obtained. The true importance and functionality of Eq. (29F) to The Input/Loss Method, or any other combustion equation used for any of the Input/Loss methods, lies in the fact that consistency of molar balances is required for successful system understanding, for conservation of mass flows and for resolution of fuel chemistry. For clarity the following major terms are associated with system stoichiometrics of Eq. (29F):
Eq. (29F) describes at least three features of critical importance when determining fuel chemistry using one of the Input/Loss methods. The critical features include: 1) its ability to address air pre-heater leakage through application of the Air Pre-Heater Leakage Factor, RAct, and through the Air Pre-Heater Dilution Factor, β; 2) the ability to describe effluent concentrations on either side of the air pre-heater, again through application of RAct; and 3) the use of an explicit φAct term allowing for variable O2 concentration in the system's local combustion air. Air pre-heater leakage dilutes all combustion effluents with moist air from the local environment, thus all important effluents H2O, CO2 and O2 used for this invention are altered. Furthermore, many times, although not always, a power plant's more precise effluent measurements may be found on the air pre-heater's inlet (economizer outlet or Boiler), and not at the air heater outlet (or Stack); refer to
Based on these teachings, the following further explains the importance of the Air Pre-Heater Leakage Factor, RAct, and the Air Pre-Heater Dilution Factor, β, their definitions and developments and use. Consider that air in-leakage associated with a fossil-fired system, and as commonly associated with in-leakage at the system's air pre-heater, is defined by the American Society of Mechanical Engineers' Performance Test Code 4.3 (1974) as the mass of moist air leakage divided by the mass of wet combustion gas entering the air pre-heater. The wet combustion gas is taken at the gas inlet of the air pre-heater (i.e., Boiler, or economizer outlet before the air pre-heater). That is, as defined herein using Eq. (29F) nomenclature, noting that 100 moles of dry gas is the bases at the Boiler, is given by:
where, as defined above:
RAct=(Moles of CO2 entering the air pre-heater)/(Moles of CO2 leaving the air pre-heater). The expression for RAct is equivalent to (Moles of Boiler CO2) divided by (Moles of Stack CO2), noting that each of these would-be measurements is referenced to 100 moles of dry gas. The Air Pre-Heater Dilution Factor is then developed by performing a total dry gaseous effluent molar balance at the Stack, see
100 moles dry gaseous effluent at Stack=Σni+β(a+aφAct) (21)
and then solving for β: β=(100−Σni)/(a+aφAct). The stoichiometric base of Eq. (29F) implies that 100 moles of dry gaseous effluent upstream of the air pre-heater (Boiler) is given by RActΣni (thus Σni=100/RAct); therefore:
If, instead of obtaining the ratio of CO2 across the air pre-heater, the ratio of O2 is obtained, the following may then be developed:
R′Act=(Moles of O2 entering the air pre-heater)/(Moles of O2 leaving the air pre-heater).
where, converting from R′Act to RAct, using algebraic manipulations results in, when measuring Stack O2 (the term GAct):
If measuring Boiler O2 (for Eq. (24) termed g′Act):
There are, of course, a number of variations to these formulations, such as employing 100 moles of wet effluents at the Stack, thus replacing Eq. (21) with:
100 moles wet effluent at Stack=(Σni+j)+β(a+aφAct+bA) (25)
or using an oxygen base for the wet effluents at the Stack, thus: (Σni+JAct)/a+β(1.0+φAct); or using a combustion equation which is based on a mole of fuel carbon (xα4); etc. What is important to this invention, important to The Input/Loss Method, and important to any of the Input/Loss methods, is that the Air Pre-Heater Leakage Factor (RAct) allows gaseous measurements to be employed on either side of the system air in-leakage. Typically, but not always, O2 is measured in the combustion gas stream inlet to the air pre-heater (Boiler), while CO2 is measured at the Stack (downstream from the air pre-heater).
After establishing system stoichiometrics, the next stage of the process involves the recognition that because a given fuel has an unique, although unknown, chemical composition, when burned it will yield unique concentrations of principle effluents CO2, H2O, O2, and SO2 (if fuel sulfur is present). The gaseous effluent concentrations are used to compute the fuel chemistry, with this chemistry fuel calorific value and boiler efficiency are then computed, in turn this information allows the computation of fuel flow and system efficiency. The gaseous effluents from any fossil combustion process are N2, CO2, H2O, O2 and SO2 (if fuel sulfur is present). H2O, when effluent from combustion, is in its superheated phase, thus acting as a gas. The source of N2 is principally the air used to burn the fuel and has little chemical reactiveness, thus its sensitivity to the fuel's chemical composition is not significant. The use of a measured effluent N2 is not considered practical, nor can add to the matrix solution, given that fuel nitrogen is generally one of the smallest components of a fossil fuel, effluent N2 being the largest product, thus even the slightest measurement error would have an enormous influence on computed fuel chemistry. SO2 effluent concentrations are generally in the parts per million thus its impact may have minor importance, but not always.
As an intrinsic chemical relationship, the relative concentrations of carbon (α4), hydrogen (α5) and oxygen (α3) found in any fossil fuel will have significant impact on the relative concentrations of CO2, H2O and O2 found in the effluent. The concept of involving fuel oxygen in this statement is fundamentally different from '994. Considered when developing this invention was an “Oxy-Hydrocarbon” (OHC) approach to stoichiometrics—not a simple “hydrocarbon” approach—and this being possible only through multi-variant analysis of fossil fuels (explained below). The CO2, H2O and O2 effluents will be influenced by the following: O2 used to burn the fuel (i.e., the Air/Fuel ratio); fuel water, α2; in-leakage of water including tube leaks (bZ); and water in the combustion air (bA). This implies that the molar fractions of CO2, H2O and O2 present in the effluent (the system's boundary, i.e., data at the Stack or data translated from air pre-heater inlet to the Stack) must be unique relative to the supplied fuel and supplied combustion air.
The following elemental molar balances may be derived from the combustion equation, Eq. (29F). The Γk expressions are simply convenient groupings of quantities, principally comprising measured effluents (known values) which have the greatest influence on the individual fuel elements of interest. Many coal-fired units use supplementary firing with gaseous fuel or fuel oil. Such minor fuel terms, e.g., composite gaseous fuels described by α0[CYRHZR], not shown in Eq. (29F) but taught in '994, may be included within Γk expressions and are multiplied, initially, by an estimated fuel moles, xMAF. Such minor terms may be quickly resolved when converging on xMAF. Given these groupings, the Γk expressions of Eqs. (36) through (41), with solution of the moles of combustion oxygen (the term “a”) as discussed below, may be treated as known quantities. The elemental wet fuel components are considered unknowns, as are the fuel moles; the unknowns include the following: α1, α2, α3, α4, α5, α6, α10 and “x” in Eq. (29F).
In these relationships the subscript “Act” means an effluent measurement or assumption (an “actual” value). The term JAct in Eqs. (37), (38) and (39) relating to the moles of effluent H2O could be input as a constant value or measured or otherwise obtained. All other values in Eqs. (36) through (41) are either measured, evaluated explicitly based on input data, internal models and/or have minor import but are carried in the formulations for teaching consistency of stoichiometrics.
Eq. (29F) teaches that fuel sulfur is allowed to produce both SO2 and SO3. For the SO2 produced from fuel sulfur a portion is allowed to be captured by effluent ash or converted by limestone. The following relationships explain, resulting in Eq. (41); refer to the DEFINITIONS section above for meanings of the variables employed in Eq. (42). From a simple sulfur balance using Eq. (29F):
Therefore by reducing Eq. (42) using the above relationships, Eq. (41) results, it employing either known quantities, or measurable quantities or quantities which may be reasonably estimated knowing the particular thermal system. It will become apparent that prior methods as taught in '994, where fuel sulfur may have been assumed constant, are not adequate for the present invention. When sulfur is present in the fuel, the genetics of the fossil fuel allow its explicit computation.
As a group, these relationships are of critical importance for understanding The Input/Loss Method. If fuel chemistry is to be resolved, thus calorific value, boiler efficiency, accurate fuel flow and system efficiency, then stoichiometric relationships generally represented by Eqs. (30) to (41) must be resolved. These equations are not unique in their grouping of terms; further reductions and/or complexities are certainty possible. The grouping of terms adopted here principally follows from the right-side of Eq. (29F).
Eqs. (30) through (34) yield five equations with nine unknowns. For this situation, unknowns include α1 through α6, α10, and the terms “a” and “x”. The term “x” is a convenience term and could be divided through changing the base of Eq. (29F) to unity moles of fuel, thus eliminating use of xαj terms comprising two unknowns. However, if done, then the effluent's base becomes per mole of fuel, e.g., thus an effluent term dAct/x, adding a different complexity involving the normalization of effluent measurements. Although the requirement ΣαMAF-j=1.00 is a convenience, it affords another, and viable, equation. By making a molar nitrogen balance, and assuming 100 moles of dry gaseous effluent at the boundary, the “a” quantity (moles of combustion oxygen) may be resolved independent of Eq. (30), thus reducing the unknowns; detailed below. Again, the entire combustion equation, Eq. (29F), could be divided through by α4, or xα4, thus setting a carbon base. Effluent N2 could be resolved by difference assuming 100 moles of gaseous effluent (CO2, H2O, O2, SO2, the minor pollutants being measured or assumed), or N2 could be measured directly. However, using effluent N2 to resolve fuel nitrogen, al, is not practical given fuel nitrogen is typically a minor fuel constituent (as is sulfur), any error made in measuring effluent N2 would greatly effect all fuel constituents; it is not a practical equation. Or, further still, by assuming constant values for fuel nitrogen and sulfur, α1 and α6, with resolution of “a”, and say: α3=1.0−ΣαMAF-j, j≠3, the system is reduced to three equations with four unknowns; these include Eqs. (31) through (33), with α2, α4, α5 and “x”. As another example, if α3 is assumed constant, then the combined Eqs. (31) and (32) (with cancellation of xα2) represents one equation with two unknowns, “x” and α5. And, of course, further reductions and manipulations of unknowns and equations is entirely possible. However, the point is that close examination of the physical problem of combustion stoichiometrics, in which fuel chemistry is to be determined from effluents, indicates that the mathematical system has more unknowns than equations. In summary, these manipulations are discussed to emphasize that, as taught by this invention, a new approach must be provided which provides, not mere simple correlations of hydrogen versus carbon as was done in '994, but rather establishing the genetics of the fossil fuel. '994 solution employed, that was believed to be intrinsic chemical relationships, correlation constants within the resolution of the combustion equation (i.e., single-variant correlation constants appear within stoichiometric equations). Although '994 employed single-variant correlations based on MAF molar concentrations, single-variant correlations based on weight concentrations are commonly found throughout the fossil fuel literature.
To address the solution problem, whereas the '994 solution was achieved through relationships found between MAF molar fuel hydrogen and MAF molar fuel carbon (and representing a particular mined fuel), the present invention recognizes the genetics of the fossil fuel and employs its findings to achieve a matrix solution. The Preferred Embodiment does not require that the minor fuel constituents be assumed constant, they may be measured quantities (e.g., effluent SO2, effluent CO, effluent NOX, etc.) and/or otherwise obtained. Further, as will become apparent, the Preferred Embodiment allows use of multidimensional minimization techniques taught in '877 which addresses instrumentation errors.
Returning to the solution problem as posed by Eq. (29F), the problem is solved, in part, by reducing αj quantities to a MAF molar basis, eliminating the influence of the two components not chemically involved with the Oxy-Hydrocarbon fuel per se, water and mineral matter (ash). Before addressing the genetics of fossil fuels, the following teaches how fuel water and fuel ash are resolved, the αMAF-i terms required are then fully taught in subsequent sections. MAF molar fuel water is resolved by adding Eqs. (31) and (32), then substituting xMAF for ΓCO2/αMAF-4; see Eq. (92):
αMAF-2=2[αMAF-4(ΓH2O+ΓO2)/ΓCO2−αMAF-5−αMAF-3]/3 (42)
To determine fuel ash using explicit relationships requires examination of the total system. The only system effect of fuel ash is as a pure dilutive or concentrative influence on fuel, and of course on the fuel's calorific value. From a qualitative viewpoint, as fuel ash increases at the expense of carbon (for example), the amount of combustion air required to produce the same effluent O2 actually increases given that more fuel is required to achieve the same energy flow to the working fluid given less combustibles in the fuel; in large commercial power plants the coal is borne by combustion air to the furnace region. Given a decreasing calorific value (higher ash) increased fuel flow is required to meet the same energy flow to the working fluid. Thus an ideal system parameter for such sensitivities, which is routinely measured at fossil-fueled systems, is the indicated Air/Fuel ratio. Generally such sensitivities are reasonable, a 10 percent increase in ash for a common coal will cause a linear effect in the Air/Fuel ratio. The wet, mass base, Air/Fuel ratio (termed AFAct), a calculational quantity, is developed as follows:
AFAct=(mAir+mMoisture)/mAF (48A)
AFAct=(1+β)[(a+aφAct)NAir+bANH2O]/(xNAF) (48B)
Expanding the term xNAF in Eq. (48B), noting that NAF relates to the wet As-Fired fuel (i.e., j=1, 2, 3, 4, 5, 6, 10):
xNAF=x(Σj=1−6Njαj+Njαj+N10α10) (49)
and then employing the following definitions of MAF fuel moles and fuel constituents:
xMAF≡x/(1.0+αMAF-2+αMAF-10) (50)
αMAF-j≡αj(1.0+αMAF-2+αMAF-10) (51)
allows substitution of Eqs. (50) and (51) into Eq. (49) for x and ai, cancelling the term (1.0+αMAF-2+αMAF-10) as intended, and then substituting into Eq. (48B) yields a solvable form:
xNAF=xMAF(Σj=1−6NjαMAF-j+N10αMAF-10) (52)
AFAct=(1.0+β)[(a+aφAct)NAir+bANH2O]/[xMAF(Σj=1−6NjαMAF-j+N10αMAF-10)] (53)
Simplifying Eq. (53) and solving for MAF fuel ash, αMAF-10, yields the following results. Note in Eq. (54) that a normalized Air/Fuel ratio is used, becoming AFAct, normalized to indicated plant data, defined by Eq. (57). xMAF is substituted using Eq. (56).
αMAF-10=[ΓAshαMAF-4/(ΓCO2N10)]−Σj=1−6NjαMAF-j/N10 (54)
where:
ΓAsh≡(1.0+β)[(a+aφAct)NAir+bANH2O]/AFAct (55)
xMAF=ΓCO2/αMAF-4 (56)
AFAct≡AFinput(AFRef1/AFRef2) (57)
a=(ΓN2−xMAFαMAF-1)/φAct (58)
The variable AFinput is the wet Air/Fuel ratio from the system's data collection device (an indicated value); the ratio (AFRef1/AFRef2) is used to scale AFinput. The value of N10 in Eq. (54) is input as a constant, or fitted as a function of αMAF-10 (thus solving a quadratic equation), or fitted as a function of HHVMAF. Note that a system's indicated plant fuel flow measurement could obviously be used in place of AFAct, applying similar techniques as demonstrated in determining αMAF-10. However, use of an AFAct variable is preferred since it integrally involves effluent and combustion air terms (through ΓCO2, ΓN2 and ΓAsh), and thus through such dependencies allows error analysis techniques to be operational and practical. It is noteworthy that the explicit procedure of determining fuel ash, and through use of the term (1.0+αMAF-2+αMAF-10) of Eqs. (50) and (51), allows any errors made in fuel water, αMAF-2, to be off-set by fuel ash, αMAF-10. This must occur since any given quantity xαj (wet-base) must be equivalent to xMAFαMAF-j (MAF-base); if not, such wet to MAF conversions would numerically cause inconsistencies in the computed Air/Fuel ratio.
In summary, MAF fuel ash, αMAF-10, may be determined from the explicit solution taught by Eq. (54). By “explicit solution” is meant that only independent (known) variables appear on the right hand side of an equation, including Eq. (54), the dependent term on the left (e.g., the αMAF-10 term). However, if the typical fossil fuel has no, little or essentially constant fuel ash, then αMAF-10 may be held constant, including zero. Further, it has been found that for certain lignite fuels, fuel ash may be determined by knowing, or estimating, MAF calorific value. For Greek lignite and lignite A, the following has been found broadly descriptive:
αMAF-10=0.4534−1.5199×10−5HHVMAF-EST; for kJ/kg (60A)
αMAF-10=0.4534−3.5352×10−5HHVMAF-EST; for Btu/lbm (60B)
The estimated MAF calorific value, HHVMAF-EST, may be reasonably constant especially for the poorer fuels, eliminating iterative procedures. On the other hand, the MAF molar fuel ash value for the poorer quality fuels has been found to be remarkably constant. In addition, as taught in '994, fuel ash instruments are available which determine on a dry basis the concentration of fuel ash. Thus a fuel ash concentration may be selected from the group consisting of: a constant value of fuel ash, a predictable value of fuel ash, a measured value of fuel ash determined from a fuel ash instrument and a value of fuel ash determined from explicit solution, as an obtained fuel ash concentration. The Preferred Embodiment is to determine MAF molar fuel ash from the explicit solution, Eq. (54). If however data required for Eq. (54) is missing, or fuel ash is not sufficiently variable, then the reasonable Preferred Embodiment is to hold MAF molar fuel ash constant.
As taught in the above three paragraphs, fuel water and fuel ash may be explicitly determined provided the MAF fuel chemistry is known, that is known αMAF-1, αMAF-3, αMAF-4, αMAF-5 and αMAF-6. Fuel water is dependent on αMAF-4, αMAF-5 and αMAF-3. Fuel ash, if determined using Eq. (54), is dependent on all fuel constituents less ash, including αMAF-2 of Eq. (42), “a” of Eq. (58), xMAF, etc. as indicated. The following section teaches the genetics of fossil fuels, through which the complete fuel chemistry is resolved. Note that if the minor fuel constituents of sulfur, nitrogen and ash can be assumed constant (including zero), then the matrix solution need only consider MAF molar fuel oxygen, carbon and hydrogen; thus an Oxy-Hydrocarbon understanding of the fuel.
Genetics of Fossil Fuels
The teachings of '994 relied on simple single-variant correlations to provide missing equations. As discussed above, single-variant correlations have been shown, for many important fuels, as not being adequate. What was discovered using Irish peat data (having significant fuel oxygen), was that multi-variant analysis not only dramatically improved R2 values, but improved R2 values to the point that a base understanding of the genetics of fossil fuels is obtained. What was discovered was that the following multi-variant relationships have a profound ability to describe fossil fuels with unheard of accuracy; an accuracy which addresses the very genetics of fossil fuels.
αMAF-4+αMAF-5=JOHC1+KOHC1αMAF-3 (61)
αMAF-4+αMAF-3=JOHC2+KOHC2αMAF-5 (62)
αMAF-5+αMAF-3=JOHC3+KOHC3αMAF-4 (63)
In these relationships, fuel hydrogen is taken in the diatomic form (H2), as is fuel oxygen (O2); as αMAF-5 and αMAF-3 result from Eq. (29F). This assumption, versus the monatomic, does not affect the outcome. The predictability of Eq. (63) versus '994 technology is best observed by comparing the Irish peat of
The data of
The predictability of these equations is seen in
αMAF-3−KOHC3αMAF4+αMAF-5=JOHC3 (64)
The consistency observed in the above TABLES is also observed in a wide collection of fuel samples, depending on which multi-variant analysis is chosen.
The genetics of a fossil fuel of interest, if a viable concept, should allow specification of the chemical construct of its Rank. Indeed, it should be consistent enough to be used to specify a coal's Ranks based on Ultimate Analysis results. To produce such findings, note that Eqs. (61), (62) and (63) represent three equations and three unknowns: the molar ratios of carbon to molecular hydrogen, to molecular oxygen. Solving for these equations (using data from TABLE 2, TABLE 3 and TABLE 4) results in specification of what a particular fossil fuel Rank truly means. TABLE 6 presents results for such analysis, presented by a generic chemical makeup: CHc2Oc3 where the molar constants c2 and c3 are normalized to one mole of carbon. The consistency of TABLE 6 is apparent and belays the notion of separative analyses of TABLE 2, TABLE 3 or TABLE 4 data. TABLE 6 employs ASTM D388 defined Ranks, which is not to be taken as limiting the application. For example, TABLE 6 indicates that the poorer lignites and Irish peat fuels, at the MAF level, are more “friendly” toward the environment that the higher energy coals (an & sa) in that less effluent CO2 is produced per burnt carbon. This would suggest more research towards reducing lignite's mineral matter (Irish peat has little mineral matter), and reducing the water content in these traditionally poor fuels. Using the type of data contained in TABLE 2, TABLE 3 and TABLE 4 to develop chemical makeups also will define the occasional strange fuel. One such fuel is Bear Canyon coal, although mined in the Powder River Basin it is not a PRB coal (its data is not part of
The consistency of TABLE 6 suggests that these findings be used to over-check laboratory Ultimate Analyses. The LECO Corporation, St. Joseph, Mich. state in the U.S. manufacture laboratory equipment which is used to determine Ultimate Analyses. Their equipment includes the LECO CHN 600 instrument for determining elemental carbon (C), hydrogen (H) and nitrogen (N). Their LECO CHN 132 instrument determines elemental sulfur (S). The PerkinElmer Inc., Wellesley, Md. state in the U.S. manufactures a Model 2400 Series II CHNS/O Analyzer for elemental carbon, hydrogen, nitrogen, sulfur and oxygen (by difference). These instruments would benefit when analyzing coal samples by incorporating the teachings associated with TABLE 6. Many such analyzers run in an automatic fashion, analyzing a number of samples at the same time and thus convenient to form multi-variant relationships resulting in similar data to that found in TABLE 2, TABLE 3 and TABLE 4. A data processing device would then reduce such data to a CHc2Oc3 form or its equivalence. The ability of the laboratory to report data outliers associated with such analyses would greatly improve diagnostics when testing coal samples; and would assist in discovery of unique fuels (such as Bear Canyon coal). Specifically, this invention consists of a data processing device for evaluating Ultimate Analysis data, the device comprising: a) a data acquisition device to collect data from the thermal system including at least a selection of Choice Operating Parameters, the data acquisition device producing a set of acquired system data; b) a computer with a processing means; c) a set of instructions for configuring the processing means to determine a fuel chemistry of the fossil fuel and to receive as input the set of acquired system data, resulting in a programmed computer; d) means by which the programmed computer receives as input the set of acquired system data; e) the programmed computer producing the fuel chemistry of the fossil fuel; and f) means for reporting the fuel chemistry of the fossil fuel to assist in the operation of the thermal system. Further, the invention also comprises a means to compare an Ultimate Analysis with a set of descriptive fossil fuel data based on the genetics of fossil fuels organized by categories (such as TABLE 6) including instructions to identify outlier Ultimate Analysis data. The following notes apply: 1) “a set of ultimate analysis instruments” means one or more than one instrument, examples of such instruments are cited above; 2) oxygen is typically computed by difference (i.e., 0 is produced by 1.0 minus C, H, N and S); 3) elemental concentrations are typically provided as weight fractions, conversion to molar is taught through Eqs. (94) & (93); 4) “a data processing” may be any one of the following: a device integrated within the ultimate analysis instrument, a common personal computer, a specialized computer, a hand-held computer, or an integrated circuit; and 5) the “genetics of fossil fuels” is a defined concept (its descriptive material being taught throughout this disclosure, e.g., Eqs. (61), (62), (63), (72),
The consistency of multi-variant analyses leading to the genetics of fossil fuels, has proven definitive for a wide variety of fuels, but also has proven indicative of poor industrial practices when obtaining Ultimate Analyses. As demonstrated, multi-variant analysis is definitive for the following coals, lignites and peat: an, sa, sub A, Powder River Basin, sub B, sub C, lig A, Greek lignite (lig B), and Irish peat. However, such findings as these have not been found universal. The research supporting this invention has found that the volatile Ranks of coal (lvb, mvb, hvAb, hvBb and hvCb) do not produce high R2 values when using analyses produced by laboratories following ASTM procedures. The reason for this is aggressive heating of laboratory samples performed before Ultimate Analyses which drives off hydrogen-base materials which are not tested. Although the R2 values for such fuels are considerably higher when using multi-variant analysis, results are not satisfying given the high accuracy results discovered for non-volatile fuels. For MAF molar fuel carbon plus MAF molar fuel oxygen versus MAF molar fuel hydrogen R2 values include: 88.35% for lvb; 91.44 for mvb; 84.51% for hvAb; 73.92% for hvBb; and 69.72% for hvCb. The database considered for
L10 Factor
Taught in '994 via its Eq. (72) is use of a “fuel factor”. Taught in '877, U.S. Pat. No. 6,651,035, U.S. Pat. No. 6,745,152, application US2004/128111 and application WO2003/091881 all via an Eq. (72A-alt), is use of a “L Factor” for correction of effluent errors and for use in the detection of tube failures in steam generators. Both the “fuel factor” of '994, and the “L Factor” of '877, etc. are the same quantity, herein defined as the L5 Factor. Taught in U.S. Pat. No. 6,560,563 is the use of an “L Factor”. Taught in U.S. Pat. No. 6,691,054 is the use an “F Factor”. Prior to the development of the present invention, the L5 Factor was found adequate as a descriptive quantity which, when plotted as a function of MAF molar fuel diatomic oxygen, could be normalized in such a manner as to produce a constant value. A corrected and constant L5 Factor (L5-corr) proved useful when incorporated with a number of inventions associated with The Input/Loss Method. However, when used with Irish peat, Powder River Basin coals and High Seas coals, the L5 Factor showed poor correlation. Thus in parallel with the development of the genetics of fossil fuels, and guided by that development, a new L Factor was discovered, termed the L10 Factor, which indicates a high degree of predictability for a wide range of fuels, including Irish peat, Powder River Basin coals and High Seas coal. Its corrected value, L10-corr, is essentially constant. The L10 Factor is defined by the following, common units of measure being (mass of dry effluent)/(mass of MAF fuel):
L10≡[xDRY-theorNDRY-Fuel+aDRY-theor(1.0+φRef)NAir−JtheorNH2O−xDRY-theorαDRY-10NAsh]/(xMAF-theorNMAF-Fuel) (70)
This form is taken to accent combustion moisture and ash terms (versus a direct effluent calculation). Note that Eq. (70)'s nomenclature follows Eq. (29F), but where a dried fuel is burned theoretically, producing no effluent O2, nor pollutants; and divided by the mass of moisture-ash-free fuel per the stoichiometric base. Note that xDRY-theor is the moles of dried fuel based on theoretical combustion; NDRY-Fuel is the molecular weight of dried fuel; aDRY-theor is the moles of ambient dry air required to theoretically combust the dried fuel; etc.
When L10 is plotted against either MAF molar fuel diatomic oxygen or the sum of MAF molar fuel carbon plus MAF molar fuel diatomic hydrogen, a high degree of predictability is found.
L10=GOHC1+HOHC1αMAF-3 (71)
L10=GOHC2+HOHC2(αMAF-4+αMAF-5) (72)
The regression constants, GOHCk and HOHCk, for a number of Ranks, are presented in TABLE 7 and TABLE 8. Note that
L10-corr≡L10+[−HOHC2(αMAF-4−αMAF-4-Ref+αMAF-5−αMAF-5-Ref)] (73)
where the reference values of the fuel (αMAF-4-Ref and αMAF-5-Ref) are arbitrarily chosen, but should generally reflect the actual fuel and its reference MAF calorific value.
Perhaps as expected from '877 teachings, L10 is linear with MAF molar fuel diatomic oxygen, but also linearity is achieved with MAF molar fuel carbon plus MAF molar fuel diatomic hydrogen (as lead by multi-variant analysis). Thus Eqs. (71) and (72) may be equaled for a given group of fuels, forming an independent equation to be used in the matrix solution as based on the multi-variant relationship of Eq. (72):
−ξL1αMAF-3+αMAF-4+αMAF-5=ξL2 (74)
where:
ξL1≡HOHC1/HOHC2 (75)
ξL2≡(GOHC1−GOHC2)/HOHC2 (76)
Determining Complete As-Fired Fuel Chemistry
The mathematical description of the thermal system used to obtain a complete As-Fired fuel chemistry is principally described by Eqs. (30) through (34), (42), (54) and (58), all using the combustion equation Eq. (29F); details afforded in the above teachings are included. In addition, the mathematical description of the thermal system used to obtain a complete As-Fired fuel chemistry includes the teachings of this section (six paragraphs). As taught above, the genetics of fossil fuels based on multi-variant analysis has justified two independent equations which add to the matrix solution. Returning to the stoichiometrics of Eqs. (30) through (34), the following add to the 3×3, 4×4 or 5×5 matrix solution (explained below). If twice Eq. (32) is subtracted from Eq. (31), substituting for “x” via Eq. (33) results in an expression applicable for a 3×3 matrix solution:
−2αMAF-3−ξC1αMAF-4+αMAF-5+0.0=0.0 (77)
where:
ξC1≡(ΓH2O−2ΓO2)/ΓCO2 (78)
For the sulfur term, combining Eq. (34) and (33) results in an expression applicable for the 4×4 or 5×5 matrix solution:
+0.0+ΓSO2αMAF-4+0.0−ΓCO2αMAF-6+0.0=0.0 (79)
In addition, an expression applicable for the 5×5 matrix solution is developed by substituting terms of Eq. (42) into Eq. (38) such that the term xMAFαMAF-6 is incorporated into the combined Eqs. (31) & (32); reducing terms yields:
−2αMAF-3−ξS1αMAF-4+αMAF-5+2αMAF-6+0.0=0.0 (80)
where:
ξS1≡ΓH2O−2ΓOHS−2ξS6)/ΓCO2 (81)
ξS6≡kAct[ΓSO3/(1.0−ΓSO3)]/(2ΓESP)+bPLS[σ/2−1.0−γ+σz/2+σΓSO3/(2.0−2ΓSO3)] (82)
Also, the sum of all MAF molar constituents becomes applicable for the 5×5 matrix solution as it allows solution for fuel nitrogen (αMAF-1):
αMAF-3+αMAF-4+αMAF-5+αMAF-6+αMAF-1=1.0 (83)
It becomes obvious then that the following five equations having five unknowns (an Ultimate Analysis) may be resolved in conventional fashion using a 5×5 matrix solution:
From genetics (based on L10), Eq. (74):
−ξL1αMAF-3+αMAF-4+αMAF-5+0.0+00=ξL2
From genetics, Eq. (64):
+αMAF-3/2−KOHC3αMAF-4+αMAF-5/2+0.0+0.0=JOHC3
From stoichiometrics, Eq. (80):
−2αMAF-3−ξS1αMAF-4+αMAF-5+2αMAF-6+0.0=0.0
From stoichiometrics, Eq. (79):
+0.0+ΓSO2αMAF-4+0.0−ΓCO2αMAF-6+0.0=0.0
From stoichiometrics (MAF balance), Eq. (83):
+αMAF-3+αMAF-4+αMAF-5+αMAF-6+αMAF-1=1.0.
However, the above system of equations may be reduced given situations unique to a given thermal system. If little fuel nitrogen is present (or it is highly predictable), then four equations having four unknowns (an Ultimate Analysis less nitrogen) may be resolved in using a 4×4 matrix solution, nitrogen being held constant or equated to (1.0−Σj=1,3,4,5 αMAF-j):
From genetics (based on L10), Eq. (74):
−ξL1αMAF-3+αMAF-4+αMAF-5+0.0=ξL2
From genetics, Eq. (64):
+αMAF-3/2−KOHC3αMAF-4+αMAF-5/2+0.0=JOHC3
From stoichiometrics, Eq. (77):
−2αMAF-3−ξC1αMAF-4+αMAF-5+0.0=0.0
From stoichiometrics, Eq. (79):
+0.0+ΓSO2αMAF-4+0.0−ΓCO2αMAF-6=0.0.
Further, if both fuel nitrogen and fuel sulfur are either highly predictable (and/or the fuel contains no sulfur), then three equations having three unknowns comprising the base Oxy-Hydrocarbon model as an intrinsic out-come of the genetics of fossil fuels, may then be resolved using a 3×3 matrix solution. Specifically, sulfur may be held constant, including zero, or resolved via Eq. (34) after determining a 4 from the 3×3 matrix solution.
From genetics (based on L10), Eq. (74):
−ξL1αMAF-3+αMAF-4+αMAF-5=ξL2
From genetics, Eq. (64):
+αMAF-3/2−KOHC3αMAF-4+αMAF-5/2=JOHC3
From stoichiometrics, Eq. (77):
−2αMAF-3−ξC1αMAF-4+αMAF-5=0.0.
Such collections of equations for the aforementioned matrix solutions are certainly not unique, to one skilled several variations will become apparent given any study. For example the above 3×3 matrix solution obviously may invoke Eq. (83) such that its right-hand side is constant; i.e., known and constant nitrogen (αMAF-1) and sulfur (αMAF-6):
From genetics, Eq. (64):
+αMAF-3−KOHC3αMAF-4+αMAF-5=JOHC3
From stoichiometrics, Eq. (77):
−2αMAF-3−ξC1αMAF-4+αMAF-5=0.0
From stoichiometrics (MAF balance), Eq. (83):
+αMAF-3+αMAF-4+αMAF-5=(1.0−αMAF-1−αMAF-6)
As another example, the 4×4 matrix solution may also employ the MAF balance of Eq. (83), replacing the L10 relationship, by setting αMAF-1 constant; the right-hand side of Eq. (83) becoming (1,0-αMAF-1) after re-arranging. Although the 5×5 matrix solution, involving all MAF fuel constituents, is the Preferred Embodiment, the ERR-CALC and HEATRATE programs are provided with an input option which selects which of these matrix solutions is to be employed. Such selection is based principally on the predictability of the nitrogen and sulfur fuel components (e.g., knowing whether the fuel has sulfur); of course when employing the 5×5 matrix solution, such judgement is not required. In summary, the operator of the thermal system or a vendor selling to said operator may be using the genetics of the fossil fuel based on multi-variant analysis as taught herein, and may be using a mathematical description of the thermal system as taught herein to improve the system. On the other hand, the operator of the thermal system or a vendor selling to said operator may be developing the genetics of the fossil fuel based on multi-variant analysis as taught herein and may be developing a mathematical description of the thermal system based on the teachings herein to improve the system.
Once the Ultimate Analysis of MAF fuel constituents is resolved, MAF fuel moles may be computed from Eq. (56): xMAF=ΓCO2/αMAF-4. With the Ultimate Analysis of MAF fuel constituents known, with MAF fuel water of Eq. (42) and, with xMAF, AFAct and “a”, MAF fuel ash of Eq. (54) may then be resolved in an explicit manner. To summarize, the matrix solutions presented in the preceding four paragraphs employ results from the genetics of the fossil fuel, based on multi-variant analysis, and employ mathematical description of the thermal system based on stoichiometrics. Terms are not mixed. The features incorporated into the matrix solutions presented in the preceding three paragraphs—representing a considerable inventive step beyond '994 include:
Thus all fuel constituents, and the fuel moles, are therefore determined on a MAF basis. From these values, the wet base molar fuel fractions are then determined, as are the wet base moles of fuel (x) and the wet base (As-Fired) weight fractions (WFj) of all fuel constituents j:
αj=αMAF-j/(1.0+αMAF-2+αMAF-10) (90)
x=xMAF(1.0+αMAF-2+αMAF-10) (91)
xαj≡xMAFαMAF-j (92)
WFj=αjNj/(ΣαjNj) (93)
WFDRY-j=WFj/(1.0−WF2) (94)
Determining Calorific Value, Boiler Efficiency, Fuel and Effluent Flows
This section includes the mathematical description of the thermal system used to obtain a calorific value, boiler efficiency, fuel and effluent flows. Having obtained a complete As-Fired fuel chemistry, the fuel's calorific value (i.e., heating value) is next computed. Following the teachings of '994, calorific value is determined based on a differential analysis. References are cited in '994. Note that the term NMAF is the molecular weight of the MAF-base fuel (without fuel water and without fuel ash).
For calorific value units of measure in kJ/kg:
ΔHHVMAF-delta=HHVMAF-Ref−(−414928.58αMAF-3+427034.81αMAF-4+181762.20αMAF-5+297011.59αMAF-6)Ref/NMAF-Ref (98A)
HHVMAF-uncorr=(−414928.58αMAF-3+427034.81αMAF-4+181762.20αMAF-5+297011.59αMAF-6)Actual/NMAF-Actual (99A)
For calorific value units of measure in Btu/lbm:
ΔHHVMAF-delta=HHVMAF-Ref−(−178387.18αMAF-3+183591.92αMAF-4+78143.68αMAF-5+127692.00αMAF-6)Ref/NMAF-Ref (98B)
HHVMAF-uncorr=(−178387.18αMAF-3+183591.92αMAF-4+78143.68αMAF-5+127692.00αMAF-6)Actual/NMAF-Actual (99B)
HHVMAF═HHVMAF-uncorr+ΔHHVMAF-delta (100)
HHVDRY═HHVMAF(1.0−WFDRY-10) (101)
HHVAF═HHVDRY(1.0−WF2) (102)
The preferred correlations used to determine calorific values for the present invention are based on chemical binding energies. Studies have demonstrated that traditional correlations, such as the Mott-Spooner correlation based on Dulong's formula—well known in the industry—are not adequate. The Preferred Embodiment of the present invention requires at least the coefficients used in determining calorific value to fall within certain ranges associated with three principal constituents of coal. Studies have indicated that using the above preferred constants, which fall within the required ranges, reduces the standard deviation of five dozen wildly varying coal analyses from ±530 to ±214 ΔkJ/kg (±228 to ±92 ΔBtu/lbm, i.e., ΔBtu/pound). The ranges of these coefficients, i.e., multiples the molar fractions αj in Eqs. (98A) and (99A), for units of kJ/kg, or their equivalent weight fractions (for this presentation of ranges, the symbol WFj represents percent weight of j), include the following: for carbon molar fraction 390358αcarbon/Nfuel to 429994αcarbon/Nfuel, or in weight percent carbon, 325WFcarbon to 358WFcarbon; for hydrogen molar fraction 180623αhydrogen/Nfuel to 293109αhydrogenNfuel assuming the diatomic hydrogen, or in weight percent hydrogen, 896WFhydrogen to 1454WFhydrogren; and for also for oxygen molar fraction −275190αoxygen/Nfuel to −579178αoxygen/Nfuel assuming diatomic oxygen, or in weight percent oxygen, −86WFoxygen to −181WFoxygen. These ranges are independent of the fuel base, whether MAF, dry or As-Fired fuel constituents are used. Also, the ranges of these coefficients, i.e., multiples the molar fractions αj in Eqs. (98B) and (99B), for units of Btu/lbm, or their equivalent weight fractions (for this presentation of ranges, the symbol WFj represents percent weight of j), include the following: for carbon molar fraction 168154αcarbon/Nfuel to 184969αcarbon/Nfuel, or in weight percent carbon, 140WFcarbon to 154WFcarbon; for hydrogen molar fraction 77611αhydrogen/Nfuel to 125993αhydrogen/Nfuel, assuming diatomic hydrogen, or in weight percent hydrogen, 385WFhydrogen to 625 WFhydrogen; and for the oxygen molar fraction −118396αoxygen/Nfuel to —249591αoxygen/Nfuel assuming diatomic oxygen, or in the weight percent oxygen, −37WFoxygen to −78WFoxygen. These ranges are independent of the fuel base, whether MAF, dry or As-Fired fuel constituents are used.
Boiler efficiency is defined as either gross calorific based, ηB-HHV (i.e., higher heating value, HHV), or net calorific based, 71B-LHV (i.e., lower heating value, LHV). In the Preferred Embodiment boiler efficiency is determined using the methods of '429. Another of the Input/Loss methods may be used to determine boiler efficiency, provided consistency between boiler efficiency, fuel flow and effluent flow is maintained. The details of such consistency is thoroughly discussed in '994. In addition to '429, the following procedures for determining boiler efficiency have sufficient accuracy and consistency for use by this invention: the American Society of Mechanical Engineers' (ASME) Performance Test Codes (PTC) 4.1 and 4; the German standard “Acceptance Testing of Steam Generators, DIN 1942, DIN DEUTSCHES Institut Fur Normung E.V., February 1994; the European standard (draft) prEN 12952-15:1999 (also: CEN/TC 269/WG 3 N 337), “Water-Tube Boilers and Auxiliary Installations—Part 15: Acceptance Tests”, November 1999, European Committee for Standardization, Central Secretariat, rue de Stassart, 36, Brussels; and the British Standard “Code for Acceptance Tests on Stationary Steam Generators of the Power Station Type”, BS 2885:1974, ISBN: 0 580 08136 2.
As taught in '429, and considered important for this invention, is that the As-Fired fuel flow compute identically from either efficiency base:
For Eq. (103), such computations, if following the Preferred Embodiment, required that: 1) the Firing Correction term HBC be employed; 2) the calorific values be properly corrected, if needed, for a constant pressure process (resulting in HHVP or LHVP); and 3) the calorimetric temperature, TCal, be consistently employed in all terms making up boiler efficiency. All of these teachings may be found in '429. However, this invention is not limited to the use Eq. (103) and the HBC term (although preferred), as many of the industrial standards to set HBC to zero and use methods other than '429 to compute boiler efficiency; the important criteria is to maintain consistency of use when determining fuel flow, effluent flow, etc. based on boiler efficiency, BBTC and calorific value.
Knowing the complete As-Fired fuel chemistry leads to a high accuracy boiler efficiency, a boiler efficiency which in-turn leads to system efficiency. The systems' over-all thermal efficiency is defined in a consistent manner, as taught in '994. System thermal efficiency is also expressed in-terms of heat rate, HR (kJ/kWh or Btu/wKh, i.e. Btu/kilowatt-hour), the reciprocal of efficiency with units conversion.
For heat rate units of kJ/kWh:
HRHHV=3600.0000/ηSYS-HHV (106A)
HRLHV=3600.0000/ηSYS-LHV (106B)
For heat rate units of Btu/kWh:
HRHHV=3412.1416/ηSYS-HHV (107A)
HRLHV=3412.1416/ηSYS-LHV (107B)
By knowing the complete As-Fired fuel chemistry and the As-Fired fuel flow, and using a mathematical description of the thermal system based on stoichiometrics, individual effluent flows, mspecies-i (kg/hr or lb/hr), may then be determined:
mspecies-i=mAFΦiNi/(xNAF) (108)
where Φi is the moles of an effluent species on a dry-basis; i.e., Φi is the effluent concentration in moles. The term Φi derives directly from solutions or measurements of the right-hand terms of Eq. (29F), for example ΦSO2=kAct. To determine the total effluent flow, Eq. (108) may be summed, noting that ΣΦi=100.0 moles. Individual emission rates, termed ERi, in units of measure following those of reciprocal calorific value (kg-effluent/million-kJ, or pounds-effluent/million-Btu of fuel energy input), is given by the following:
As seen, an individual emission rate may be evaluated independently of the As-Fired fuel flow, Eq. (109B). However, the computational accuracy of the fuel flow, as determined using the present approach, intrinsically affects an individual emission rate through HHVAF, x and NAF. Further, the process described herein allows the determination of total effluent dry volumetric flow, at standard conditions of gaseous effluent, denoted by VF, as required by environmental regulations. VF is determined by the following (in standard-m3/sec or standard-ft3/hr):
VF=ρgasmAFNgas/(xNAF) (110)
where ρgas and Ngas are the standard density and average molecular weight of the effluent dry gas.
Correction of Choice Operating Parameters and System Benchmarking
This section includes the mathematical description of the thermal system used to obtain a multidimensional minimization analysis. This invention recognizes that those products from combustion which are used to determine a complete As-Fired fuel chemistry, as measured by routine power plant instrumentation, may have error associated with their signals. As taught herein, quantities employed to determine fuel chemistry consist not only of the principle effluents CO2, H2O and O2 but also the Air Pre-Heater Leakage Factor, etc. This invention has defined Choice Operating Parameters (COP) as all parameters which may directly impact system stoichiometrics, and thus may impact the determination of fuel chemistry. To correct errors in COPs one of two methods may be employed: 1) apply judgement based on a power engineer's experience with a particular instrument (e.g., plot signals vs. time, compare multiple signals reading the same value, etc.); and 2) use the methods as taught in '877. For the Preferred Embodiment, '877 methods are herein modified as follows. First, the use of the L Factor as a System Effect Parameter (SEP) must not employ L5, but L10 as defined via Eq. (70). Second, '877 methods must recognize that the relative humidity associated with the combustion air represents a significant sensitivity to system stoichiometrics when employing the methods of this invention. Third, a modified Objective Function has shown to be better suited the genetics of fossil fuels. In the Preferred Embodiment, COPs may be selected by the power plant engineer from any combination or all of the following:
Λ1S=dAct; Stack CO2 (with effects from Air Pre-Heater leakage) (111S)
Λ1B=dActRAct; Boiler CO2 (without effects from Air Pre-Heater leakage) (111B)
Λ2S=JAct≡j+bAβ; Stack H2O (with H2O from Air Pre-Heater leakage) (112S)
Λ2B=jRAct; Boiler H2O (without H2O from Air Pre-Heater leakage) (112B)
Λ3=AF; Air/Fuel ratio (for explicit determination of fuel ash) (113)
Λ4=RAct; Air Pre-Heater Leakage Factor (114)
Λ5=AAct; Concentration of O2 in the combustion air (115)
Λ6=mLS; System's indicated plant limestone flow (116)
Λ7S=GAct≡g+aβ; Stack O2 (with Air Pre-Heater leakage) (117S)
Λ7B=gRAct; Boiler O2 (without Air Pre-Heater leakage) (117B)
Λ8=mT; Tube leakage flow rate (118)
Λ9=HAct; Relative humidity of ambient air local to the thermal system (119)
Selecting one or more of the Choice Operating Parameters for use must depend on common understanding of power plant stoichiometrics and associated relationships to physical equipment. What the ERR-CALC program produces (
λL≡[(L10−L10-Ref)/L10-Ref]M
λW≡[(mAF−mAF-PLT)/mAF-PLT]M
λH≡[(HHVAF−HHVAF-Ref)/HHVAF-Ref]M
In these equations The Objective Function most useful for the methods and apparatus of this invention is given by Eq. (121). Note that the Bessel function of the first kind of order zero (J0) is highly suited to the sensitivities found in coal-fired stoichiometrics.
F({right arrow over (x)})=ΣkεK{Si[1.0−J0(λL)]MC
In Eq. (121), the symbol MCk is termed a Dilution Factor (as introduced in '877), but here assigned individually by COP allowing greater stability in solution. In Eq. (121) Sk is a scaling factors accounting for differing magnitudes of λj. In Eq. (121), the symbol ΣkεK indicates a summation on the index k, where k variables are contained in the set K defined as the elements of {right arrow over (Λ)}. For example, assume the user has chosen the following: Λ1S is to be optimized to minimize the error in L10 and HHVAF, Λ2S is optimized for L10 and mAF (MW=1.40), Λ4 is optimized for L10, and Λ7B is optimized for L10. Therefore: {right arrow over (Λ)}=(Λ1S, Λ2S, Λ4, Λ7B), K={Λ1S, Λ2S, Λ4, Λ7B}, thus {right arrow over (x)}=(x1, x2, x3, x4); x1=S1Λ1S; x2=S2Λ2S; x3=S3Λ4; x4=S4Λ7B; where Eq. (121) for this example then becomes:
F({right arrow over (x)})=S1{[1.0−J0(λL)]MC
+S2{[1.0−J0(λL)MC
+S3[1.0−J0(λL)]MC
Upon optimization, COP correction factors (Ck) are determined simply as: Ck=Λk/Λ0-k. Note that the only output from ERR-CALC are correction factors.
The consistency demonstrated herein by the genetics of the fossil fuels, as implemented by this invention for the determination of fuel chemistry, has proven of such remarkable consistency and accuracy that, it is believed, ambient relative humidity may offer a vehicle through which a power plant's monitoring system may be benchmarked. This statement is saying that a system's stoichiometrics (i.e., fuel chemistry versus effluent production of CO2, H2O, O2, etc., determined by The Input/Loss Method) may be verified using an independent parameter associated with combustion, ambient relative humidity, which is not directly influenced by the understanding (or not) of fuel chemistry, fuel flow and boiler efficiency. However, a relative humidity computed by The Input/Loss Method is indeed greatly affected by fuel chemistry, an understood system stoichiometrics and calorific value; such sensitivity on the computed is extreme. As a practical application, use of this benchmarking technique would verify reported carbon emissions based on the monitoring system's ability to replicate an environmental parameter which would be measured by all parties, both regulator and the system operator. Of course other air psychrometric parameters such as specific humidity, web bulb temperature, etc. might be used, but relative humidity as ranging from 0.0 to 100% is most convenient for '877 optimization procedures.
The procedure for benchmarking an on-line monitoring system is thus: 1) monitor the power plant such that SEP for the plant's indicated plant fuel flow is invoked, optimizing on both the COP for effluent H2O (Λ2S), and the COP for relative humidity (Λ9); 2) set to a constant the input of relative humidity to The Input/Loss Method; 3) ERR-CALC, using '877 methods modified as above, will produce correction factors for both Λ2S and Λ9; 4) bias the plant's indicated plant fuel flow until the corrected relative humidity computed by The Input/Loss Method agrees with a directly measured (and independent) value. When agreement is reached, fuel chemistry, fuel calorific value (CV, dependent on fuel chemistry), boiler efficiency (dependent on fuel chemistry and CV) and the energy flow to the working fluid heated by combustion products (BBTC) all must be accurate. Given this, all emission flows, e.g., carbon emission, must be accurately computed; it may be nothing else. As an example of such benchmarking
Calculational Engine Apparatus for Input/Loss Methods
Obtaining a complete As-Fired fuel chemistry, including fuel water and fuel ash (as based on: a) using a genetics of the fossil fuel based on multi-variant analysis; b) using a mathematical description of the thermal system; c) measuring a set of measurable Operating Parameters, including at least effluent concentrations of O2 and CO2, these measurements being made at a location downstream of the heat exchanger/combustion region of the thermal system; d) obtaining an effluent concentration of H2O, as an obtained effluent H2O; e) obtaining a fuel ash concentration selected from the group consisting of: a constant value of fuel ash, a predictable value of fuel ash, a measured value of fuel ash determined from a fuel ash instrument and a value of fuel ash determined from explicit solution, as an obtained fuel ash concentration; f) obtaining a concentration of O2 in the combustion air local to the system; and g) obtaining the Air Pre-Heater Leakage Factor), may be incorporated into a fuel chemistry determining apparatus to improve the understanding of fossil-fueled thermal systems, including a produced output provided from associated analytical models dependent on fuel chemistry. The produced output from the apparatus includes the fuel's calorific value (CV, dependent on fuel chemistry), boiler efficiency (dependent of fuel chemistry and CV), fuel flow per Eq. (103), and system efficiency of Eqs. (104) & (105). The produced output from the apparatus thereby provides a means to assist the operator of the thermal system in the monitoring and improvement of system efficiency on a continuous operating basis such as would be used for the on-line monitoring of power plants.
In summary, this invention includes an apparatus for assisting the operation of a thermal system burning a fossil fuel, the apparatus comprising: a) a data acquisition device to collect data from the thermal system including at least a selection of Choice Operating Parameters, the data acquisition device producing a set of system acquired data; b) a computer with a processing means; c) a set of instructions for configuring the processing means to determine a fuel chemistry of the fossil fuel and to receive as input the set of system acquired data, resulting in a programmed computer; d) means by which the programmed computer receives as input the set of system acquired data; e) the programmed computer producing the fuel chemistry of the fossil fuel; and f) means for reporting the fuel chemistry of the fossil fuel to an operator of the thermal system. The aforementioned computer may be a common personal computer, or, broadly, any data processing unit. In addition, set of instructions for configuring the processing means to determine a fuel chemistry of the fossil fuel includes programming the teachings of this invention including the genetics of the fossil fuel, the mathematical description of the thermal system, determination of an Ultimate Analysis of the fossil fuel, and determination of a complete As-Fired fuel chemistry.
Although the present invention has been described in considerable detail with regard to certain Preferred Embodiments thereof, other embodiments within the scope and spirit of the present invention are possible without departing from the general industrial applicability of the invention. For example, the descriptions of this invention assume that a steam generator's working fluid is water, however the general procedures of this invention may be applied to any type of working fluid provided that the working fluid is definable at the boundary of the system. Examples of other working fluids are: mixtures of water and organic fluids, organic fluids, liquid metals and so forth. Further, the concept of multi-variant analysis leading to the genetics of fossil fuels was presented with two elements (combinations of carbon, hydrogen and oxygen), which is the Preferred Embodiment. However, this invention is not to be limited by this concept. Multi-variant analysis leading to the genetics of fossil fuels may well employ three elements in any combination: carbon, hydrogen, oxygen and sulfur. For example, Eq. (61) might be replaced with: αMAF-4+αMAF-5+αMAF-6=J′OHC1+K′OHC1αMAF-3; thus forming a (carbon+hydrogen+sulfur) fit versus oxygen. Indeed, success has been had with such employments. Accordingly, the general theme and scope of the appended claims should not be limited to the descriptions of the Preferred Embodiment disclosed herein.
Although a Preferred Embodiment of the present invention has been demonstrated via THE DRAWINGS and described in considerable detail the foregoing DESCRIPTION OF THE PREFERRED EMBODIMENT, it will be understood that the invention is not limited to the embodiments disclosed, but those methods are capable of numerous rearrangements, modifications and substitutions without departing from the scope and spirit of the present invention as set forth and defined by the claims herein.
The
Within fossil-fired systems, some quantities are readily measured with adequate accuracy, and others may not be measured on-line (in real time) with accuracy sufficient to quantify the operation of the system 20 to the required accuracy to optimize efficiency. For example, working fluid flows, pressures and temperatures may be readily measured with good accuracy by conventional sensors located at defined boundaries such as 134, 130, 25, 33, 42, 29 and 31. Choice Operating Parameters all may, under ideal conditions, be directly measured with common industrial accuracy either in real time or periodically, then corrected using the methods of '877 if required. In