Method for fuel flow determination and improving thermal efficiency in a fossil-fired power plant

• US 5,367,470 A
• Filed: 02/12/1992
• Issued: 11/22/1994
• Est. Priority Date: 12/14/1989
• Status: Expired due to Term

• Current Assignee: Exergetic Systems LLC
• Original Assignee: Exergetics Systems, Inc.
• Inventors: Lang, Fred D.
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): ZANELLI, MICHAEL J
• Application Number:
  US07/835,719
• Time in Patent Office: 1,014 Days
• Field of Search: 364/509, 364/510, 364/498, 364/499, 364/494, 364/557, 364/148, 364/152, 364/153, 73/23.31, 73/23.32, 73/25.01, 73/204.18, 374/43, 431/12
• US Class Current: 700/274
• 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

A method for determining fuel flow rate, pollutant flow rates, and boiler efficiency for a fossil-fired steam generator system from an analysis of the composition of the dry fuel base and composition of the combustion effluents.

Claims

1. A method for improving thermal efficiency of a fossil-fired power plant system comprising a boiler cycle in which a fossil fuel is supplied at a flow rate to be combusted 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 of the combustion process, the temperature, concentrations of CO₂ and H₂ O effluents to an accuracy of at least ±

0.5% molar, and concentrations of 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 a boiler absorption efficiency based on determination of non-stack losses,

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

determining an efficiency of the turbine cycle,

combining the boiler efficiency and the turbine cycle efficiency to obtain the power plant system efficiency,

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

adjusting operation of the system to improve its boiler efficiency and/or its system efficiency.

2. The method of claim 1 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 boiler efficiency and/or system efficiency.

3. The method of claim 1 wherein the measured CO₂ and H.sub. O effluents are measured by utilizing an emissions spectral radiometer.

4. The method of claim 1 including determining whether degradations of operation are occurring in the boiler cycle, and whether stack losses are increasing by detecting decreases in iterative combustion efficiency determinations.

5. The method of claim 1 including determining whether degradations of operation are occurring in the boiler cycle due to increased radiation and convection losses, heat content remaining in the coal rejects if the fuel is coal, heat exchanger water/steam leaks, heat exchanger loss of effectiveness, and increases in other non-stack losses by detecting decreases in iterative boiler absorption efficiency determinations.

6. A method for determining and improving thermal efficiency of a fossil-fired power plant system comprising a boiler cycle in which a fossil fuel is supplied at a flow rate to be combusted 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, comprising the following steps:

analyzing the fuel for its dry base chemical composition,

measuring in the exhaust of 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 ±

0.5% molar by utilizing an emissions spectral radiometer, and concentrations of 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 mass flow rate, both

a combustion efficiency as based on a stoichiometric balance of a combustion equation and a boiler absorption efficiency based on determination of non-stack losses,

combining combustion efficiency and boiler absorption efficiency to obtain the boiler 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 boiler 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 boiler absorption efficiency calculations, and

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

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

analyzing the fuel for its dry base chemical composition,

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

0.5% molar, and concentrations of 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,

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

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

determining the fuel flow rate from the boiler efficiency.

8. The method of claim 7 including 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.

9. The method of claim 7 further comprising the following steps:

measuring the concentration of the common pollutants in the exhaust of the combustion process with an accuracy comparable to standard industrial practice, and

determining the pollutant flow rates from the fuel mass flow rate and knowledge of the concentrations of the common pollutants.

10. The method of claim 9 wherein the common pollutants are measured by utilizing an emissions spectral radiometer.

11. The method of claim 9 wherein action is taken to adjust operation of the steam generator system to minimize pollutant concentrations effluent from the steam generator system by lowering the fuel firing rate, by mixing fuels having different sulfur contents for SO₂ and SO₃ control, by lowering the combustion flame temperature for NO_x control and other such actions necessary to reduce pollutant concentrations.

12. The method of claim 9 wherein action is taken to adjust operation of the steam generator system to minimize pollutant effluent flow rates from the steam generator system by lowering the fuel firing rate, by mixing fuels having different sulfur contents for SO₂ and SO₃ control, by lowering the combustion flame temperature for NO_x control, by mixing fuels having different nitrogen contents for NO_x control, and other such actions necessary to reduce pollutant flow rates.

13. The method for determining fuel flow rate and pollutant flow rates of claim 9 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.

14. The method according to claim 7 further comprising the steps of determining a calculated heating value of the fuel based on the dry base chemical composition of the fuel and an assumed water content of the fuel, and repetitiously changing the assumed water concentration in the fuel until consistency is obtained between the measured water concentration in the fuel and the computed water concentration in the fuel, thereby establishing validity for the calculated heating value of the fuel.

15. A method for determining fuel flow, pollutant flow rates, and improving thermal efficiency of a fossil-fired steam generator power plant system comprising a boiler cycle in which a fossil fuel is supplied at a flow rate to be combusted 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 a boiler absorption efficiency based on determination of non-stack losses,

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

determining an efficiency of the turbine cycle,

combining the boiler efficiency and the turbine cycle efficiency to obtain the power plant system efficiency,

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

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

16. The method according to claim 15 in which the concentrations of CO₂ and H₂ O effluents are measured to a predetermined accuracy of greater than ±

5.0% molar.

17. The method according to claim 15 in which the concentrations of CO₂ and H₂ O effluents are measured to a predetermined accuracy of greater than ±

0.5% molar.

18. The method according to claim 15 further comprising the step of determining the fuel flow rate from the boiler efficiency.

19. The method according to claim 15 further comprising the steps of

measuring the concentration of the common pollutants in the exhaust of the combustion process with an accuracy comparable to standard industrial practice and

determining the pollutant flow rates from the fuel mass flow rate and knowledge of the concentrations of the common pollutants.

20. The method according to 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 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 power plant system efficiency.