Methods and systems for improving thermal efficiency, determining effluent flows and for determining fuel mass flow rates of a fossil fuel fired system

• US 5,790,420 A
• Filed: 11/21/1994
• Issued: 08/04/1998
• Est. Priority Date: 12/14/1989
• Status: Expired due to Term

• Current Assignee: Exergetic Systems LLC, Not Exerget, Inc.
• Original Assignee: Not Exerget, Inc.
• Inventors: Lang, Fred D.
• Primary Examiner(s): Trammell, James P.
• Assistant Examiner(s): Bui, Bryan
• Application Number:
  US08/344,541
• Time in Patent Office: 1,352 Days
• Field of Search: 364/494, 364/483, 364/498, 364/148, 364/510, 60/39.03, 60/39.05, 60/39.5, 60/39.01, 60/39.182, 60/39.461, 60/39.02, 60/670, 429/12, 429/19, 429/26, 73/23.31, 73/25.01, 423/212, 423/235, 423/237
• US Class Current: 700/287
• CPC Class Codes: F23N 2005/185 using detectors sensitive to rate of flow of fuel
• CPC Class Codes: F23N 2221/10 Analysing fuel properties, e.g. density, calorific
• CPC Class Codes: F23N 2225/22 heat losses
• CPC Class Codes: F23N 2239/02 Solid fuels
• CPC Class Codes: F23N 5/003 using detectors sensitive to combustion gas properties F23N5/02, F23N5/18 - F23N5/26 take precedence
• CPC Class Codes: F23N 5/18 using detectors sensitive to rate of flow of air or fuel

Abstract

Methods and systems are disclosed for: (1) determining and improving the thermal efficiency of a fossil fuel power plant, such as a combustion turbine system, by indirect assessment of input fossil fuel flow rate, and direct observation of various gaseous effluents; (2) determining total effluent gas flow rates; (3) determining input fuel mass flow rates; and (4) determining flow rates of various constituent gases making up the effluent gas.

Claims

1. A method for improving a thermal efficiency of a fossil fuel fired system, comprising the steps of:

(a) analyzing a sample of a fossil fuel supplied to a combustor of a fossil fuel fired system to determine the composition of the fossil fuel;

(b) measuring a temperature of a gas effluent from the combustor, wherein the effluent gas comprises a mixture of constituent gases;

(c) measuring a concentration of a gaseous constituent of the gas effluent from the combustor;

(d) determining a thermal efficiency of the system;

(e) comparing the thermal efficiency of the system to a reference thermal efficiency; and

(f) adjusting an operation of the system to improve its thermal efficiency and/or its system efficiency.

2. The method of claim 1, wherein the fossil fuel fired system is a combustion turbine system.

3. The method of claim 2, wherein the combustion turbine system system efficiency is determined by a method comprising the steps of:

(a) determining a combustion efficiency;

(b) determining an absorption efficiency; and

(c) combining the combustion efficiency and the absorption efficiency, to thereby determine a combustion turbine system system efficiency.

4. The method of claim 2, wherein the combustion turbine system thermal efficiency is determined independently of a fuel flow rate of a fossil fuel supplied to the combustor.

5. The method of claim 2, wherein the sample of a fossil fuel is analyzed for its dry base chemical composition.

6. The method of claim 2, wherein a constituent gas is carbon dioxide, and the temperature and concentration of carbon dioxide in the gas effluent from the combustor is measured.

7. The method of claim 6, wherein the concentration of the carbon dioxide gas effluent from the combustor is measured to an accuracy of at least about ±

1% Δ

molar.

8. The method of claim 7, wherein the concentration of the carbon dioxide gas effluent from the combustor is measured to an accuracy of at least about ±

0.5% Δ

molar.

9. The method of claim 2, wherein a constituent gas is superheated water, and the temperature and concentration of superheated water in the gas effluent from the combustor is measured.

10. The method of claim 9, wherein the concentration of the superheated water effluent from the combustor is measured to an accuracy of at least about ±

1% Δ

molar.

11. The method of claim 2, wherein a constituent gas is oxygen and the concentration of oxygen in the gas effluent from the combustor is measured.

12. The method of claim 11, wherein the concentration of the oxygen gas effluent from the combustor is measured with an accuracy at least comparable to zirconium oxide detection.

13. A method for improving a thermal efficiency of a combustion turbine system, comprising the steps of:

(a) analyzing a sample of a fossil fuel supplied to a combustor of a combustion turbine system to determine the dry base chemical composition of the fossil fuel;

(b) measuring at a gas exit boundary of the combustion turbine system in an exhaust from the combustion process;

(i) a temperature of a gas exiting the combustion turbine,

(ii) a concentration of gaseous carbon dioxide to an accuracy of at least about ±

0.5% Δ

molar,

(iii) a concentration of a superheated water effluent to an accuracy of at least ±

1% Δ

molar, and

(iv) a concentration of a gaseous oxygen effluent with an accuracy at least comparable to zirconium oxide detection;

(c) determining, independently of a fuel flow rate of a fossil fuel into the combustor, a combustion efficiency;

(d) determining an absorption efficiency;

(e) combining the combustion efficiency and the absorption efficiency to determine a combustion turbine system system efficiency;

(f) comparing the combustion turbine system efficiency to a reference combustion turbine system efficiency; and

(g) adjusting an operation of the combustion turbine system to improve its thermal efficiency and/or its system efficiency.

14. The method of claim 13, wherein the combustion turbine system comprises a heat recovery-steam generator system.

15. A method for improving a thermal efficiency of a combined heat recovery-steam generator and combustion turbine system, comprising the steps of:

(a) analyzing a sample of a fossil fuel supplied to a combustor of a combustion turbine system to determine the composition of the fossil fuel;

(b) measuring a temperature and concentration of a combustion gas effluent from the combustor;

(c) measuring a net energy deposition and power developed from the combustion gas;

(d) determining independently of a fuel flow rate of a fossil fuel into the combustor, a combustion efficiency based upon a stoichiometric balance of a combustion equation and an absorption efficiency based upon a measurement of a non-stack heat loss;

(e) combining the combustion efficiency and the absorption efficiency to determine a combined heat recovery-steam generator and combustion turbine system system efficiency;

(f) comparing the combined heat recovery-steam generator and combustion turbine system efficiency to a reference combined heat recovery-steam generator and combustion turbine system efficiency; and

(g) adjusting an operation of the combined heat recovery-steam generator and combustion turbine system to improve a thermal efficiency and/or a system efficiency of the combined heat recovery-steam generator and combustion turbine system.

16. The method of claim 15, wherein the sample of a fossil fuel is analyzed for its dry base chemical composition.

17. The method of claim 15 including the steps of repetitiously adjusting an assumed water concentration in the fuel until consistency is obtained between the measured CO₂ and H₂ O effluents and computed CO₂ and H₂ O effluents determined by stoichiometrics based on the chemical composition of the fuel, thereby establishing the validity of the calculated combustion turbine thermal efficiency and/or total system efficiency.

18. The method of claim 15, wherein the measured carbon dioxide and water effluents are measured by using an emissions spectral radiometer instrument.

19. The method of claim 15 including determining whether degradations of operation are occurring in the recovery boiler or in the combustion turbine, and whether stack losses are increasing, by detecting decreases in combustion efficiency which is determined in an iterative manner.

20. The method of claim 15 including determining whether degradations of operation are occurring due to increased radiation and convection losses, heat content remaining in the heat exchanger water/steam leaks, heat exchanger loss of effectiveness, and increases in other non-stack losses by observing decreases in iterative absorption efficiency calculations.

21. A method for determining and improving a thermal efficiency of a fossil-fuel combustion turbine system comprising a combustion turbine in which a fossil fuel is supplied at a flow rate to produce shaft power, the combustion of the fuel producing an effluent combustion gas in an exhaust, the effluent combustion gas from the combustion turbine being capable of heating a working fluid, and a turbine cycle in which the working fluid does work, comprising the following steps:

analyzing the fuel for its dry base chemical composition,

measuring in the exhaust combustion gas from the combustion process at the gas exit boundary of the power plant system the temperature, concentrations of CO₂ and H₂ O effluents to at least an accuracy of ±

1% Δ

molar, and concentrations of O₂ with an accuracy at least comparable to zirconium oxide detection,

measuring a shaft power produced,

determining, independently of the fuel mass flow rate, both a combustion efficiency as based on a stoichiometric balance of a combustion equation and an absorption efficiency based on determination of non-stack losses,

combining combustion efficiency and absorption efficiency to obtain a combustion turbine system system efficiency,

repetitiously adjusting assumed water concentration in the fuel until consistency is obtained between the measured CO₂ and H₂ O effluents and those determined by stoichiometries based on the chemical concentration of the fuel for establishing validity for a calculated fuel mass flow rate and boiler efficiency,

determining whether degradations from predetermined parameters are occurring in the fuel-air mixing equipment, the differential system fuel flows, the heat content of the fuel, and whether stack losses are increasing by detecting decreases in iterative combustion efficiency calculations,

determining whether degradations from predetermined parameters are occurring due to increased radiation and convection losses, heat content remaining in the coal rejects, heat exchanger water/steam leaks, heat exchanger loss of effectiveness, and increases in other non-stack losses by detecting decreases in iterative absorption efficiency calculations, and

adjusting operation of the combustion turbine system to improve its thermal efficiency and/or its system efficiency.

22. A method for determining a fuel flow rate and pollutant flow rates of a fossil fuel fired system by monitoring the operation of the system and making calculations which are derived from data obtained from the analysis of the chemical composition of a dry component of the fuel, concentrations of common pollutants produced from combustion, and concentrations of CO₂ and superheated water produced from combustion of the fuel, the method comprising the steps of:

analyzing the fuel for its dry base chemical composition,

measuring at a gas exit boundary of the system in the exhaust of the combustion process the temperature, concentrations of CO₂ and H₂ O effluents to an accuracy of at least ±

1% Δ

molar, and concentrations of O₂ with an accuracy at least comparable to zirconium oxide detection,

measuring the net energy deposition to a working fluid being heated by the combustion process,

calculating, independently of the fuel flow rate, a combustion efficiency based on the stoichiometric balance of a combustion equation and an absorption efficiency based on determination of non-stack losses,

combining the combustion efficiency and the absorption efficiency to obtain a system efficiency, and

determining the fuel flow rate from the system efficiency.

23. The method of claim 22, wherein the fossil fuel fired system is a combustion turbine system.

24. The method of claim 22, further comprising the steps of repetitiously changing the assumed value of water concentration in the fuel until consistency is obtained between the measured CO₂ and H₂ O effluents and computed CO₂ and H₂ O effluents determined by stoichiometries based on the chemical composition of the fuel, thereby establishing validity for the calculated fuel mass flow rate.

25. The method of claim 22, wherein the measured carbon dioxide and water effluents are measured by using an emissions spectral radiometer instrument.

26. The method of claim 22 wherein action is taken to adjust operation of the system to minimize pollutant concentrations effluent from the system by selecting an action from the group consisting of lowering the fuel firing rate, mixing fuels having different sulfur contents for SO₂ and SO₃ control, lowering the combustion flame temperature for NO_X control, and mixing fuels having different nitrogen contents for NO_X control.

27. The method for determining a fuel flow rate and pollutant flow rates of claim 22 including the steps of repetitiously changing an assumed value of water concentration in the fuel until consistency is obtained between the measured CO₂ and H₂ O effluents and the computed CO₂ and H₂ O effluents determined by stoichiometries based on the chemical composition of the fuel, thereby establishing validity for the calculated pollutant flow rates.

28. A method for determining fuel flow, total effluent flow rate, and individual pollutant flow rates, and improving thermal efficiency of a fossil-fired steam generator power plant system comprising a steam generator system in which a fossil fuel is supplied at a flow rate to be combusted to produce shaft power and/or to heat a working fluid, the combustion of the fuel producing effluents in an exhaust, and a turbine cycle in which the working fluid does work, the method comprising the following steps:

analyzing the fuel for its dry base chemical composition,

measuring at a gas exit boundary of the power plant system, in the exhaust, the temperature, the concentrations of CO₂ and H₂ O effluents to a predetermined accuracy, and O₂ with an accuracy at least comparable to zirconium oxide detection,

measuring the net energy deposition to the working fluid being heated by the combustion process,

determining, independently of the fuel flow rate, a combustion efficiency based on a stoichiometric balance of a combustion equation and an absorption efficiency based on determination of non-stack losses,

combining the combustion efficiency and the absorption efficiency to obtain a system efficiency,

determining an auxiliary turbine efficiency,

determining a shaft efficiency;

combining the absorption efficiency, the turbine cycle efficiency, and the shaft efficiency to obtain the total system efficiency,

determining in response to obtaining the absorption efficiency and the system efficiency if either is degraded from predetermined parameters, and

adjusting operation of the power plant system to improve its absorption efficiency and/or its total system efficiency.

29. The method according to claim 28, wherein the concentration of a superheated water effluent is measured to a predetermined accuracy of at least ±

1% Δ

molar.

30. The method of claim 28, further comprising the step of determining the fuel flow rate from the absorption efficiency.

31. The method of claim 28, further comprising the steps of:

(a) measuring the concentration of the common pollutants in the exhaust of the combustion process with an accuracy comparable to standard industrial practise; and

(b) determining the pollutant flow rates from the fuel mass flow rate, knowledge of the concentrations of the common pollutants, and by determining the total effluent flow rate through stoichiometics.

32. The method according to claim 28, further comprising the steps of repetitiously adjusting an assumed water concentration in the fuel until consistency is obtained between the measured CO₂ and H₂ O effluents and the CO₂ and H₂ O effluents determined by stoichiometrics based on the chemical composition of the fuel, thereby establishing the validity of the calculated boiler efficiency and/or total system efficiency.

33. A method for determining a flow rate of an effluent gas produced by combustion of a fossil fuel, comprising the steps of:

(a) measuring a temperature of an effluent gas, wherein the effluent gas comprises a mixture of constituent gases;

(b) measuring a pressure of the effluent gas;

(c) determining a concentration of a constituent gas in the effluent gas;

(d) determining a density of the effluent gas;

(e) determining an average molecular weight of the constituent gases;

(f) determining a molecular weight of the fuel combusted;

(g) determining a molar fraction of the as-fired fuel required to generate a reference unity moles of the effluent gas; and

(h) determining an as-fired mass flow rate of the fuel combusted, thereby determining effluent gas flow rate.

34. The method of claim 33, wherein the effluent gas is produced by combustion of a fossil fuel in a system selected from a conventional boiler system, a combustion turbine system, and a combined combustion turbine system and heat recovery-steam generator system.

35. A method for determining a flow rate of a gaseous constituent of an effluent gas produced by combustion of a fossil fuel, comprising the steps of:

(a) measuring a temperature of an effluent gas, wherein the effluent gas comprises a mixture of constituent gases;

(b) measuring a pressure of the effluent gas;

(c) determining a concentration of a constituent gas in the effluent gas;

(d) determining a density of the effluent gas;

(e) determining an average molecular weight of the constituent gases;

(f) determining a molecular weight of the fuel combusted;

(g) determining a molar fraction of the as-fired fuel required to generate a reference unity moles of the effluent gas; and

(h) determining an as-fired mass flow rate of the fuel combusted, thereby determining a flow rate of the constituent gas.

36. A system for determining and improving a thermal efficiency of a combustion turbine system, comprising:

(a) apparatus for analyzing a sample of a fossil fuel supplied to a combustor of a combustion turbine system to determine the composition of the fossil fuel;

(b) apparatus for measuring a temperature of a gas effluent from the combustor, wherein the effluent gas is a mixture of constituent gases;

(c) apparatus for measuring a concentration of a constituent gas;

(d) apparatus for determining a combustion turbine system efficiency;

(e) apparatus for comparing the combustion system efficiency to a reference combustion system efficiency; and

(f) apparatus for adjusting an operation of the combustion turbine system to improve a thermal efficiency and/or a system efficiency of the combustion turbine system.

37. The system of claim 36, wherein the apparatus for analyzing a sample of a fossil fuel is selected from the group consisting of a gas chromatograph and a mass spectrometer.

38. The system of claim 36, wherein the apparatus for measuring a temperature of a gas effluent from the combustor comprises a thermocouple.

39. The system of claim 36, wherein the apparatus for measuring a concentration of a constituent gas comprises an emissions spectral radiometer.

40. The system of claim 36, wherein the apparatus for determining a combustion turbine system efficiency, for comparing the combustion system efficiency to a reference combustion system efficiency, and for adjusting an operation of the combustion turbine system to improve a thermal efficiency of the combustion turbine system comprises a programmed computer.