Patent ID: 8959917
Filing Date: 2015-02-24
Classification: F01K,F22B,F22D

Abstract:
1. A method for operating a once-through steam generator operating with sliding pressure and at a steam temperature above 650° C. and for lowering its forced-flow minimum load, the once-through steam generator being incorporated into a water/steam-carrying working medium circuit of a power station, and an economizer of the once-through steam generator having upstream, as seen in the working medium circulation direction, at least one HP preheater and one heat transfer system for preheating the working medium, the working medium absorbing heat from a supplied turbine bleed steam stream within the HP preheater or preheaters and absorbing heat from a supplied auxiliary heat stream in the heat transfer system, the method comprising: reducing, if a predetermined part load point is undershot, the heat absorption of the working medium within at least one HP preheater and the heat transfer system so that the temperature of the water/steam as a working medium at the outlet of the economizer lies at a distance of a predetermined temperature difference below the boiling temperature related to the corresponding economizer outlet pressure, wherein the reduction in heat absorption is performed by a controlling device, the supply of the auxiliary heat stream to the heat transfer system being prevented completely by the controlling device, and at least part of the water/steam working medium stream being routed past a component located in the water/steam circuit of the heat transfer system by a bypass line.