Method of operating a once-through steam generator with low load recirculation

摘要

The steam generator has a feed pump (5), an economiser (1), an evaporator (2), a water separator (3) and at least one superheater (4), as well as a circulation pipe (20) connected to the water outlet of the separator (3) and opening into the working medium flow between feed pump and economiser. Arranged between the mouth (19) of the circulation pump (20) and the economiser (1) is a circulation pump (23), as well as, behind the latter, a level control valve (24). The method for operating this steam generator consists in that, above a minimum flow-through quantity of the economiser (1), the feed quantity is adjusted depending upon the steam temperature downstream of the water separator (3) and that, below the minimum flow-through quantity of the economiser (1), the water level in the water separator (3) is regulated by operating the level control valve (24) arranged between the circulation pump (23) and the economiser (1). As a result, the otherwise usual switching from the steam temperature regulation to the water level regulation, which likewise acts on the feed water supply, and vice versa, is no longer necessary. IMAGE