C.C. AND CHP OPERATIONABILITY AND FLEXIBILITY Improving Combined Cycle flexibility: design and operating experience

摘要

Having the economic crisis led to a considerable contraction of the European energy market, Combined Cycle operating flexibility is nowadays the best lever to gain profitability on the energy market. Starting from customer requirements the following “Flexibility Packages” were identified, developed and tested by Ansaldo Energia: ? Minimum environmental load reduction (MEL): many operators ask to decrease the MEL, in order to reduce variable costs linked to fuel consumption maintaining the possibility to quick ramp up the GT engine when the payback from the grid is higher. Some operating strategies were investigated and validated on real GT engines. Special attention was paid to: anti-icing system, turbine vanes cooling air regulation, installation of CO catalyst system within the HRSG, regulating blow-off valves. ? Grid support improvement: steam turbine participation to frequency regulation has been optimized and several test campaign to increase GT loading/unloading rates has been performed. Grid support is also guaranteed in case of operation in country with high instability of grid frequency. ? Start-up time reduction and reliability increase: in order to make the engine ready to start when required from the grid, it is convenient to have reduced start up time and reliable procedure. Some tests were carried out on a real GT engine increasing the load rate from cold condition and a new Rotor Stress Evaluator has been developed for the steam turbine, resulting in a significant start up time reduction. The described MEL reduction strategy has been tested on several combined cycle power plants. The tests have been performed on AE94.3A F class gas turbine, at different ambient temperature and pressure conditions.