Method for operating a once-through steam generator and steam generator designed for carrying out the method

摘要

Method for operating a once-through steam generator (2) comprising an evaporator (4), in which a feeding mass flow (SM) of a flow medium (M) is supplied with the aid of a feed pump (12) to the evaporator (4) and at least partially evaporated there, wherein flow medium (W) that has not evaporated is separated in a separator (18) arranged downstream of the evaporator (4) and a circulating mass flow (UM) of the separated flow medium (W) is returned with the aid of a circulating pump (24) to the evaporator (4), and so the mass flow referred to as the evaporator mass flow (VM) of the flow medium (M) flowing through the evaporator (4) is additively made up of the feeding mass flow (SM) and the circulating mass flow (UM). It is thereby provided that in a low-load interval (I) the feeding mass flow (SM) is increased with increasing load (L) while the circulating mass flow (UM) is kept substantially constant, in a moderate load interval (II) the feeding mass flow (SM) is further increased with increasing load (L) and the circulating mass flow (UM) is reduced to zero, and optionally in a high load interval the feeding mass flow (SM) is further increased with increasing load (L) and the circulating mass flow (UM) is kept at zero. The invention also relates to a once-through steam generator that is particularly suitable for carrying out the method.