Fuel Consumption Index for Proper Monitoring of Power Plants - Revisited

This paper presents an method for heat rate monitoring of power plants which employs a true “systems approach”. As an ultimate monitoring parameter, derived from Second Law concepts, it quantifies system losses in terms of fuel consumption by individual components and processes. If electricity is to be produced with the least un-productive fuel consumption, then thermodynamic losses must be understood and minimized. Such understanding cuts across vendor curves, plant design, fuels, Controllable Parameters, etc. This paper demonstrates that thermal losses in a nuclear unit and a trash burner are comparable at a prime facia level. The Second Law offers the only foundation for the study of such losses, and affords the bases for a true and ultimate indicator of system performance. From such foundations, a Fuel Consumption Index (FCI) was developed to indicate specifically what components or processes are thermodynamically responsible for fuel consumption. FCIs tell the performance engineer why fuel is being consumed, quantifying that a portion of fuel which must be consumed to overcome TCycle frictional dissipation in the turbine cycle (FCI ), the combustion Comb process (FCI ), and so forth; and, indeed, how much fuel is Power required for the direct generation of electricity (FCI ). FCIs have been particularly applicable for monitoring power plants using the Input/Loss Method. FCIs, Äheat rates based on FCIs, and an “applicability indicator” for justifying the use of Reference Bogey Data are all defined. This paper also presents the concept of “dynamic heat rate”, based on FCIs, as a parameter by which the power plant operator can gain immediate feedback as to which direction his actions are thermally headed: towards a lower or higher heat rate. NOMENCLATURE j FCI = Fuel Consumption Index for any j_t _h component j or process, 'FCI = 1000; unitless. Power IMFC = Dynamic Fuel Consumption Index for Power; unitless. ~ I ~ ~ g = Specific exergy composed of physical, chemical, and thermal contributions; Btu/lbm. Fuel g = Specific exergy of As-Fired fuel; Btu/lbm. in G / Total system exergy flow and shaft power inputs; Btu/hr. Misc 'G = Miscellaneous exergy flows inlet and outlet from the system: steam-air heater, water losses, etc; Btu/hr. AF HBC / Firing Correction (i.e., “energy credit”), Btu/lbm . AF HHV = Higher heating value, laboratory determined; Btu/lbm . HHVP = As-Fired (wet-base) higher heating value corrected AF for a constant pressure process, Btu/lbm . j hr = Differential heat rate associated with any single j_t _h component or process; ÄBtu/kWh. j Ähr = Difference between two differential heat rates associated with the same j_t _h component; ÄÄBtu/kWh. HR = Unit heat rate (gross, total system); Btu/kWh. ÄHR = Difference in unit heat rate, commonly termed “unit heat rate deviation”; ÄBtu/kWh. D IMHR = Dynamic Heat Rate, ÄBtu/kWh. i I = Irreversibility for an i_t _h component or process; Btu/hr. ÄKE/m = Relative specific kinetic energy, assumed zero. ÄPE/m = Relative specific potential energy, assumed zero. Air Air m g = Total exergy of moist combustion air inlet; Btu/hr. AF m = Mass flow rate of As-Fired fuel; lbm/hr. MQ = Incremental heat transfer; Btu/hr. in Q = Heat transfer to the working fluid from boiler; Btu/hr. Rej Q = Heat transfer from the condenser tube-side to the circulatory water (i.e., local environment); Btu/hr. j SFU = Specific Fuel Usage of any j_t _h component or process, AF Äfuel flow per power; Älbm /kWh. Ref T = Temperature of reference conditions; degree F. MW = Incremental shaft power; Btu/hr. Fan 'W = Summation of shaft powers supplied to combustion gases and air (generally the FD and ID fans); Btu/hr. Pump 'W = Summation of pump shaft powers supplied to the boiler and turbine cycle; Btu/hr. output W = Gross electrical generation; Btu/hr. j (1 + Ø ) = Term used to test applicability of the Reference Bogey Data (if positive, data is applicable); unitless.