A method for operating a once-through steam generator including an evaporator, in which a feeding mass flow of a flow medium is supplied using a feed pump to the evaporator and at least partially evaporated there, wherein flow medium that has not evaporated is separated in a separator arranged downstream of the evaporator and a circulating mass flow of the separated flow medium is returned using a circulating pump to the evaporator, and the mass flow referred to as the evaporator mass flow of the flow medium flowing through the evaporator is additively composed of the feeding mass flow and the circulating mass flow. In a low-load interval, the feeding mass flow is increased with increasing load while the circulating mass flow is kept substantially constant, in a moderate load interval the feeding mass flow is further increased with increasing load and the circulating mass flow is reduced to zero.
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