the line 80 into the condenser 13 in the high pressure stage the feedwater which is at high pressure is first heated in the economizer 26 and is evaporated in the evaporator 28 which communicates through a recirculating pump 84 with the water steam separating container 58 the steam is superheated in the superheater 30 and delivered to the high pressure part 10a of the steam turbine 10 the steam which is pressure relieved or expanded there is carried together with the steam produced in the low pressure stage to the low pressure part 10b of the steam turbine 10 the parts of the system being acted upon by the hot pressure relieved flue gas rg or in other words the walls of the steam generator 15 and its built in fixtures in particular the heating surfaces 20 30 are typically constructed in such a way as to achieve high efficiency of the system for full load operation in partial load operation the capacity of the gas turbine 2 is often reduced with the consequence that the temperature t of the pressure relieved flue gas rg drops this in turn causes a decrease in the quantity of steam produced and a disproportionate reduction in the available total water quantity or feedwater flow upon a new load change and also upon startup of the gas turbine critical operating states can be attained because of the rapid rise of the flue gas temperature t or because of major temperature and or mass flow changes.