Method for detecting heat exchanger tube failures and their location when using input/loss performance monitoring of a power plant

• US 6,651,035 B1
• Filed: 10/09/2002
• Issued: 11/18/2003
• Est. Priority Date: 03/24/1998
• Status: Expired due to Fees

• Current Assignee: Exergetic Systems LLC
• Original Assignee: Exergetic Systems LLC
• Inventors: Lang, Fred D
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): Barbee, Manuel L.
• Application Number:
  US10/268,466
• Time in Patent Office: 405 Days
• Field of Search: 702/22-25, 702/30-32, 702/45, 702/50, 702/51, 702/55, 702/114, 702/181-185, 60/39, 60/24, 60/395.11, 606/61, 607/93, 700/27, 700/42, 700/86, 703/2, 706/907, 706/915, 165/11.1, 165/70, 431/22, 431/16
• US Class Current: 702/183
• CPC Class Codes: F22B 35/18 Applications of computers to steam boiler control
• CPC Class Codes: F23N 1/002 using electronic means F23N1/04 - F23N1/10 take precedence
• CPC Class Codes: F23N 2221/08 Preheating the air
• CPC Class Codes: F23N 2221/10 Analysing fuel properties, e.g. density, calorific
• CPC Class Codes: F23N 2223/40 Simulation
• CPC Class Codes: F23N 2225/22 heat losses
• CPC Class Codes: F23N 5/003 using detectors sensitive to combustion gas properties F23N5/02, F23N5/18 - F23N5/26 take precedence
• CPC Class Codes: G01M 3/3227 for radiators
• CPC Class Codes: G05B 13/042 in which a parameter or coefficient is automatically adjusted to optimise the performance

Abstract

This invention relates to a fossil-fired thermal system such as a power plant or steam generator, and, more particularly, to a method for rapid detection of tube failures and their location with the steam generator, without need for direct instumentation, thereby preventing more serious damage and minimizing repair time on the effected heat exchanger. This method is applicable to Input/Loss methods of monitoring fossil-fired thermal systems.

Claims

1. A method for quantifying the operation of a fossil-fired thermal system through knowledge of when its heat exchanger leaks working fluid into the combustion gas path producing a tube leakage, the method for quantifying the operation comprising the steps of:

monitoring the fossil-fired thermal system by one of the Input/Loss methods,

developing a mathematical model of the combustion process incorporating terms commonly associated with fossil fuel combustion and terms associated with sources of working fluid flows into the combustion gas path including tube leakage resulting in a stoichiometric model of the combustion process using a molar base, and

determining a tube leakage in moles based on the stoichiometric model of the combustion process using a molar base.

2. The method according to claim 1 further comprising the steps, after determining, of:

obtaining a molecular weight of the fossil fuel,

obtaining a molecular weight of the working fluid,

obtaining a fuel flow rate of the thermal system,

determining a tube leakage flow rate based on the tube leakage in moles, the molecular weight of the fossil fuel, the molecular weight of the working fluid, the fuel flow rate, and the stoichiometric model of the combustion process using a molar base, and

reporting the tube leakage flow rate such that corrective action may take place.

3. The method according to claim 2 further comprising the steps, after reporting, of:

identifying a set of heat exchangers descriptive of the thermal system as employed to transfer net energy flow to the working fluid from the combustion gases resulting in a set of identified heat exchangers,

obtaining a set of Operating Parameters applicable to the set of identified heat exchangers,

analyzing a set of net energy flows to the working fluid from the combustion gases based on the set of identified heat exchangers, the set of Operating Parameters and the tube leakage flow rate, each analyzed set descriptive of thermal system and wherein each analyzed set the tube leakage flow rate is assigned to a different heat exchanger, resulting in an analyzed set of heat exchangers,

determining a reference key comparative parameter for the thermal system,

obtaining a set of key comparative parameters associated with each identified heat exchanger, applicable with the reference key comparative parameter, and based on the analyzed set of heat exchangers,

determining a set of deviations between the set of key comparative parameters and the reference key comparative parameter,

determining an identification of the leaking heat exchanger based on the set of deviations, and

reporting to the operator of the thermal system the identification of the leaking heat exchanger such that corrective action may take place.

4. The method of claim 1, wherein the step of determining the tube leakage in moles comprises the steps of:

forming a hydrogen stoichiometric balance based on the stoichiometric model of the combustion process using a molar base, and

solving the hydrogen stoichiometric balance for the tube leakage in moles.

5. A method for quantifying the operation of a fossil-fired thermal system when being monitored by one of the Input/Loss methods through knowledge of when its heat exchanger leaks working fluid into the combustion gas path producing a tube leakage, the method for quantifying the operation comprising the steps of:

developing a mathematical model of the combustion process incorporating terms commonly associated with fossil fuel combustion and terms associated with sources of working fluid flows into the combustion gas path including tube leakage resulting in a stoichiometric model of the combustion process,

selecting a set of minimization techniques applicable to the thermal system and its fuel, and a set of routine inputs and convergence criteria to the minimization techniques,

selecting a Choice Operating Parameter of tube leakage flow rate,

selecting a set of routine Choice Operating Parameters,

determining a set of System Effect Parameters applicable to the thermal system and its fuel whose functionalities effect the determination of system heat rate and are sensitive to tube leakage flow rate,

determining a set of Reference System Effect Parameters applicable to the set of System Effect Parameters,

determining an objective function applicable to the thermal system'"'"'s stoichiometric situation which uses the Choice Operating Parameter of tube leakage flow rate, the set of routine Choice Operating Parameters, the set of System Effect Parameters, and the set of Reference System Effect Parameters,

optimizing the Choice Operating Parameter of tube leakage flow rate and the set of routine Choice Operating Parameters based on the mathematical model of the combustion process, the set of minimization techniques and the objective function such that convergence criteria is met resulting in a set of converged Choice Operating Parameters including the tube leakage flow rate, and

reporting the tube leakage flow rate such that corrective action may take place.

6. The method according to claim 5 further comprising the steps, after reporting, of:

determining a set of Reference Fuel Characteristics,

determining the fuel chemistry of the fuel being combusted by the thermal system using one of the Input/Loss methods, the mathematical model of the combustion process, the set of converged Choice Operating Parameters, and the set of Reference Fuel Characteristics,

determining a fuel heating value of the system based on the fuel chemistry and the set of Reference Fuel Characteristics,

obtaining a set of Operating Parameters,

determining a Firing Correction base on the set of Operating Parameters, and

determining a boiler efficiency of the thermal system independent of fuel flow based on the set of converged Choice Operating Parameters including the tube leakage flow rate, the fuel chemistry, the fuel heating value, the Firing Correction and the set of Operating Parameters.

7. The method according to claim 6 further comprising the steps, after determining the boiler efficiency, of:

determining an energy flow to the working fluid of thermal system based on the set of Operating Parameters as influenced by the tube leakage flow rate,

determining a fuel flow of the fossil fuel being combusted using the energy flow to the working fluid, the fuel heating value, the Firing Correction and the boiler efficiency, and

reporting the fuel flow as influenced by the tube leakage flow rate.

8. The method according to claim 7 further comprising the steps, after reporting, of:

determining a power output from the thermal system,

determining a system heat rate using the fuel flow, the fuel heating value, the Firing Correction and the power output from the thermal system, and

reporting the system heat rate as influenced by the tube leakage flow rate.

9. The method according to claim 7 fie comprising the steps, after reporting, of:

determining a power output from the thermal system,

determining a system heat rate using the energy flow to the working fluid, the boiler efficiency and the power output from the thermal system, and

reporting the system heat rate as influenced by the tube leakage flow rate.

10. The method of claim 5, wherein the step of selecting the set of minimization techniques applicable to the thermal system and its fuel comprises a step of:

incorporating a BFGS technique applicable to the thermal system and its fuel.

11. The method of claim 5, wherein the step of selecting the set of minimization techniques applicable to the thermal system and its fuel comprises a step of:

incorporating a Simulated Annealing technique applicable to the thermal system and its fuel.

12. The method of claim 5, wherein the step of selecting the set of minimization techniques applicable to the thermal system and its fuel comprises a step of:

incorporating a neural Rework technique applicable to the thermal system and its fuel.

13. The method of claim 5, wherein the step of selecting the set of minimization on techniques applicable to the thermal system and its fuel comprises a step of:

incorporating a Neugents technology applicable to the thermal system and its fuel.

14. The method of claim 5, wherein the step of selecting the set of minimization techniques applicable to the thermal system and its fuel comprises a step of:

incorporating a Pegasus Technology applicable to the thermal system and its fuel.

15. The method of claim 5, wherein the step of selecting the set of minimization techniques applicable to the thermal system and its fuel comprises a step of:

incorporating a NeuCo, Inc. technology.

16. The method of claim 5, wherein the step of selecting the set of routine Choice Operating Parameters comprises a step of:

determining a set of scaling factors for the set of routine Choice Operating Parameters resulting in the set of routine Choice Operating Parameters whose values are scaled.

17. The method according to claim 5 further comprising the steps, after reporting, of:

identifying a set of heat exchangers descriptive of the thermal system as employed to transfer net energy flow to the working fluid from the combustion gases resulting in a set of identified heat exchangers,

obtaining a set of Operating Parameters applicable to the set of identified heat exchangers,

analyzing a set of net energy flows to the working fluid from the combustion gases based on the set of identified heat exchangers, the set of Operating Parameters and the tube leakage flow rate, each analyzed set descriptive of the thermal system and wherein each analyzed set the tube leakage flow rate is assigned to a different heat exchanger, resulting in an analyzed set of heat exchangers,

determining a reference key comparative parameter for the thermal system,

obtaining a set of key comparative parameters associated with each identified heat exchanger, applicable with the reference key comparative parameter, and based on the analyzed set of heat exchangers,

determining a set of deviations between the set of key comparative parameters and the reference key comparative parameter,

determining an identification of the leaking heat exchanger based on the set of deviations, and

reporting to the operator of the thermal system the identification of the leaking heat exchanger such that corrective action may take place.

18. The method of claim 17, wherein the step of determining the referee key comparative parameter for the thermal system, comprises a step of:

selecting a fuel flow as the reference key comparative parameter for the thermal system.

19. The method of claim 17, wherein the step of determining the reference key comparative parameter for the thermal system, comprises a step of:

selecting a fuel water fraction as the reference key comparative parameter.

20. The method of claim 17, wherein the step of determining the reference key comparative parameter for the thermal system, comprises a step of:

selecting a heating value as the reference key comparative parameter.

21. The method of claim 17, wherein the step of determining the reference key comparative parameter for the thermal system, comprises a step of:

selecting a computed cleanliness factor for each heat exchanger as the reference key comparative parameter for the thermal system.

22. A method for quantifying the operation of a fossil-fired thermal system when being monitored on-line by The Input/Loss Method through knowledge of when its heat exchanger leaks working fluid into the combustion gas path producing a tube leakage flow rate, the method comprising the steps of:

before on-line operation,

developing a mathematical model of the combustion process incorporating terms commonly associated with fossil fuel combustion and terms associated with sources of working fluid flows into the combustion gas path including tube leakage resulting in a stoichiometric model of the combustion process, and

selecting a set of minimization techniques applicable to the thermal system and its fuel, and a set of routine inputs and convergence criteria to the minimization techniques; and

thereafter

performing a Pass 0 monitoring cycle while operating on-line which determines a trip mechanism associated with a tube leakage flow rate, comprising the steps of;

assuming a tube leakage flow rate is zero,

selecting a set of routine Choice Operating Parameters,

determining a set of System Effect Parameters applicable to the thermal system and its fuel whose functionalities effect the determination of system heat rate, and determining applicable Reference System Effect Parameters,

performing a Pass 0 monitoring cycle using The Input/Loss Method resulting in a set of fuel concentrations and correction factors to the set of routine Choice Operating Parameters,

testing the set of fuel concentrations and correction factors against a set of corresponding limits resulting in a trip mechanism indicating the stoichiometric reason how a heat exchanger may leak a tube leakage flow rate into the combustion gas path, and

assuming the trip mechanism indicates a tube leakage flow rate is possible; and

thereafter

performing a Pass 1 monitoring cycle while operating on-line which determines a tube leakage flow rate, comprising the steps of;

multiplying a value of uncorrected effluent water concentration by a reference correction factor resulting in a constant effluent water concentration,

multiplying a value of uncorrected effluent carbon dioxide concentration by a reference correction factor resulting in a constant effluent carbon dioxide concentration,

selecting a set of routine Choice Operating Parameters including tube leakage flow rate but excluding effluent water and carbon dioxide,

determining a set of System Effect Parameters applicable to the thermal system and its fuel whose functionalities effect the determination of system heat rate and are sensitive to tube leakage flow rate, and determining applicable Reference System Effect Parameters,

performing a Pass 1 monitoring cycle using The Input/Loss Method resulting in a set of converged Choice Operating Parameters including the tube leakage flow rate, and thereafter;

reporting the tube leakage flow rate such that corrective action may take place.

23. A method for quantifying the operation of a fossil-fired thermal system when being monitored by one of the Input/Loss methods through knowledge of a stoichiometric mechanism of how a heat exchanger could be leaking a tube leakage flow rate into the combustion gas path, the method for quantifying the operation comprising the steps of:

developing a mathematical model of the combustion process incorporating terms commonly associated with fossil fuel combustion and terms associated with sources of working fluid flows into the combustion gas path including tube leakage,

obtaining a set of Choice Operating Parameters,

obtaining a set of Reference Fuel Characteristics,

obtaining a fuel chemistry of the fuel being combusted by the thermal system using one of the Input/Loss methods, the mathematical model of the combustion process, the set of Choice Operating Parameters, and the set of Reference Fuel Characteristics, said fuel chemistry resulting in a set of fuel concentrations,

establishing a set of concentration limits for each fuel constituent based on Reference Fuel Characteristics,

testing the set of fuel concentrations against the set of concentration limits resulting in a trip mechanism indicating the stoichiometric reason how a heat exchanger leaks a tube leakage flow rate into the combustion gas path, and

reporting the trip mechanism to the operator of the thermal system.

24. A method for quantifying the operation of a fossil-fired thermal system when being monitored by one of the Input/Loss methods through knowledge of a stoichiometric mechanism of how a heat exchanger could be leaking a tube leakage flow rate into the combustion gas path, the method for quantifying the operation comprising the steps of:

developing a mathematical model of the combustion process incorporating terms commonly associated with fossil fuel combustion and terms associated with sources of working fluid flows into the combustion gas path including tube leakage,

selecting a set of minimization techniques applicable to the thermal system and its fuel,

processing a set of routine inputs and convergence criteria to the minimization techniques,

assuming a tube leakage flow rate is zero,

selecting a set of routine Choice Operating Parameters,

determining a set of System Effect Parameters applicable to the thermal system and its fuel whose functionalities effect the determination of system heat rate,

determining a set of Reference System Effect Parameters applicable to the set of System Effect Parameters,

determining an objective function applicable to the thermal system, the set of routine Choice Operating Parameters, the set of System Effect Parameters and the set of Reference System Effect Parameters,

optimizing the set of routine Choice Operating Parameters based on the mathematical model of the combustion process, the set of minimization techniques, and the objective function such that convergence is met resulting in a set of converged Choice Operating Parameters,

determining a fuel chemistry of the fuel being combusted by the thermal system using one of the Input/Loss methods, the mathematical model of the combustion process, the set of converged Choice Operating Parameters, and Reference Fuel Characteristics resulting in a fuel elementary composition, a fuel ash fiction and a fuel water fraction said composition and fractions resulting in a set of fuel concentrations,

establishing a set of concentration limits for the set of fuel concentrations based on Reference Fuel Characteristics,

testing the set of fuel concentrations against the set of concentration limits resulting in a trip mechanism indicating the stoichiometric reason how a heat exchanger leaks a tube leakage flow rate into the combustion gas path, and

reporting the trip mechanism to the operator of the thermal system.

25. The method of claim 24, wherein the step of establishing the set of concentration limits for the set of fuel concentrations based on Reference Fuel Characteristics and the step of testing the set of fuel concentrations against the concentration limits, comprises the steps of:

determining a set of correction factors to Choice Operating Parameters using their initial and converged values, and

establishing a set of correction factor limits for the selected Choice Operating Parameters, and testing the set of correction factors against the set of correction factor limits resulting in a trip mechanism indicating the stoichiometric reason how a heat exchanger leaks a tube leakage flow rate into the combustion gas path.

26. A method for quantifying the operation of a thermal system burning a fossil fuel in a combustion process through knowledge of when one of its heat exchangers, whose tubes contain working fluid heated by products of combustion, has a tube leak of working fluid mixing with the products of combustion, the method for quantifying the operation comprising the steps of:

selecting a neural network technology applicable to the thermal system,

selecting a set of routine inputs and database for the neural network technology,

selecting a set of Choice Operating Parameters including tube leakage flow rate,

developing a mathematical model of the combustion process incorporating terms commonly associated with a combustion process and terms associated with sources of working fluid mixing with the products of combustion including tube leakage,

obtaining a set of Reference System Effect Parameters associated with the thermal system,

calculating a set of System Effect Parameters based on the mathematical model of the combustion process,

optimizing the set of Choice Operating Parameters including tube leakage flow rate using the neural network technology, and the set of routine inputs and database, the set of Reference System Effect Parameters and the set of System Effect Parameters, such that convergence is met resulting in a set of converged Choice Operating Parameters including a tube leakage flow rate, and

reporting the tube leakage flow rate such that corrective action may take place.

27. The method of claim 26, wherein the step of selecting the neural network technology applicable to the thermal system and its fuel, comprises a step of:

selecting a Neugents technology applicable to the thermal system and its fuel.

28. The method of claim 26, wherein the step of selecting the neural network technology applicable to the thermal system and its fuel, comprises a step of:

selecting a Pegasus Technology applicable to the thermal system and its fuel.

29. The method of claim 26, wherein the step of selecting the neural network technology applicable to the thermal system and its fuel, comprises a step of:

selecting a NeuCo, Inc. technology applicable to the thermal system and its fuel.

30. A method for quantifying the operation of a fossil-fired thermal system when being monitored by one of the Input/Loss methods coincident with one of its heat exchangers leaking its working fluid into the combustion gas path producing a tube leakage flow, the method for quantifying the operation by identification of the leaking heat exchanger comprising the steps of:

identifying a set of heat exchangers descriptive of the thermal system as employed to transfer net energy flow to the working fluid from the combustion gases resulting in a set of identified heat exchangers,

obtaining a set of Operating Parameters applicable to the set of identified heat exchangers,

analyzing a set of net energy flows to the working fluid from the combustion gases based on the set of identified heat exchangers, the set of Operating Parameters and the tube leakage flow rate, each analyzed set descriptive of the thermal system and wherein each analyzed set the tube leakage flow rate is assigned to a different heat exchanger, resulting in an analyzed set of heat exchangers,

determining a reference key comparative parameter for the thermal system,

obtaining a set of key comparative parameters associated with each identified heat exchanger, applicable with the reference key comparative parameter, and based on the analyzed set of heat exchangers,

determining a set of deviations between the set of key comparative parameters and the reference key comparative parameter,

determining an identification of the leaking heat exchanger based on the set of deviations, and

reporting to the operator of the thermal system the identification of the leaking heat exchanger such that corrective action may take place.

31. The method of claim 30, wherein the step of determining the reference key comparative parameter for the thermal system, comprises a step of:

selecting a fuel flow as the reference key comparative parameter for the thermal system.

32. The method of claim 30, wherein the step of determining the reference key comparative parameter for the thermal system, comprises a step of:

selecting a fuel water fraction as the reference key comparative parameter for the thermal system.

33. The method of claim 30, wherein the step of determining the reference key comparative parameter for the thermal system, comprises a step of:

selecting a heating value as the reference key comparative parameter for the thermal system.

34. The method of claim 30, wherein the step of determining the reference key comparative parameter for the thermal system, comprises a step of:

selecting a computed cleanliness factor for each heat exchanger as the reference key comparative parameter for the thermal system.

35. A method for quantifying the operation of a thermal system burning a fossil fuel in a combustion process through knowledge of when one of its heat exchangers, whose tubes contain working fluid heated by products of combustion, has a tube leak of working fluid mixing with the products of combustion, the method for quantifying the operation comprising the steps of:

monitoring the thermal system using one of the Input/Loss methods,

developing a mathematical model of the combustion process incorporating terms commonly associated with the combustion process and terms associated with sources of working fluid mixing with the products of combustion including tube leakage,

determining a tube leakage based on the mathematical model of the combustion process, and

reporting the tube leakage such that corrective action may take place.

36. The method of claim 35, wherein the step of developing a mathematical model of the combustion process comprises the steps of:

forming a hydrogen stoichiometric balance of the combustion process including terms associated with sources of working fluid mixing with the combustion products including tube leakage, and

solving the hydrogen stoichiometric balance for the tube leakage.

37. The method of claim 35, wherein the step of monitoring the thermal system using one of the Input/Loss methods, comprises the step of:

monitoring the thermal system using The Input/Loss Method.

38. The method of claim 35, wherein the step of monitoring the thermal system using one of the Input/Loss methods, comprises the step of:

determining a fuel chemistry based on one of the Input/Loss methods.

39. The method of claim 35, wherein the step of monitoring the thermal system using one of the Input/Loss methods, comprises the steps of:

determining a fuel heating value based on one of the Input/Loss methods.

40. The method of claim 35 further comprising the steps, after reporting, of:

identifying a set of heat exchangers descriptive of the thermal system resulting in a set of identified heat exchangers,

obtaining a set of Operating Parameters applicable to the set of identified heat exchangers resulting in a set of heat exchanger data sufficient to determine net energy flow to the working fluid from the products of combustion for each heat exchanger in the set of identified heat exchangers,

calculating a net energy flow to the working fluid of the thermal system as many times as there are heat exchangers in the set of identified heat exchangers, wherein each calculation of net energy flow includes all heat exchangers in the set of identified heat exchangers, wherein for each calculation of net energy flow the tube leakage is assigned to a different heat exchanger, resulting in a set of analyzed heat exchangers based on the set of heat exchanger data,

determining a set of reference key comparative parameters,

obtaining a set of key comparative parameters associated with the set of identified heat exchangers applicable with the set of reference key comparative parameters, and based on the set of analyzed heat exchangers,

determining a set of deviations between the set of key comparative parameters and the set of reference key comparative parameters,

identifying a location of the heat exchanger within the thermal system having the tube leak based on the set of deviations, and

reporting to the operator of the thermal system the location of the heat exchanger within the thermal system having the tube leak such that corrective action may take place.

41. A method for quantifying the operation of a thermal system burning a fossil fuel in a combustion process through knowledge of when one of its heat exchangers, whose tubes contain working fluid heated by products of combustion, has a tube leak of working fluid mixing with the products of combustion, the method for quantifying the operation comprising determining a location of the heat exchanger within the thermal system with the tube leak based on the working fluid'"'"'s energy flow by assigning the tube leak to different heat exchangers.

42. The method of claim 41 further comprising:

obtaining a boiler efficiency,

obtaining a fossil fuel heating value,

obtaining a Firing Correction applicable to the thermal system, and

determining a calculated fuel flow based on the working fluid'"'"'s energy flow effected by the tube leak of working fluid, the location of the heat exchanger within the thermal system with the tube leak, the boiler efficiency, the fossil fuel heating value, and the Firing Correction.

43. The method of claim 41 further comprising:

obtaining a boiler efficiency,

obtaining a power produced from the thermal system,

determining a calculated heat rate of the thermal system based on the working fluid'"'"'s energy flow effected by the tube leak of working fluid, the location of the heat exchanger within the thermal system with the tube leak, the boiler efficiency and the power produced from the thermal system.