Adapting the Siemens/KWU steam quality guidelines to the operational boundary conditions of modern power plants (especially combined-cycle plants)

摘要

The changing power plant market has altered the demands made on operational boundary conditions for modem combined-cycle plants. The requirements made call for increasing numbers of start-ups and shorter start-up times. Nowadays some plants, particularly combined-cycle plants, must be guaranteed to withstand up to 250 starts a year. Start-up times are strictly limited. Condensate polishing systems, auxiliary boilers and thermal deaerator systems are increasingly being omitted. The Siemens steam quality guideline used to date was no longer sufficient to cover these operating requirements. New bases for evaluation had to be established to restrict increased stress caused by steam impurities. Siemens responded by defining so-called action levels which clearly stipulate maximum permitted impurity levels and the corresponding time periods.