GB1139421A - Start-up system for once through boiler - Google Patents

Abstract

1,139,421. Raising steam in forced flow once through steam generators. FOSTER WHEELER Ltd. 16 March, 1966 [17 Dec., 1964]. No. 51412/64. Heading F4A. A once-through forced flow steam generator, comprising economizer, evaporator and superheater sections 1, 2, 3 respectively connected in series, is connected to a turbine 11. The exhaust from the turbine passes to a condenser 13 from whence feed water is drawn through a de-aerater 19, by a feed pump 5 and delivered through a high pressure feed water heater 20 to the generator. During start-up and low load operation, between 30 and 60% of the flow through the evaporator surface 2 is recycled back through line 10a and mixed with cooler inlet water by pump 14, to prevent the evapo rator tubes from over-heating, the remainder of the flow passing to a steam separator 16. The water from the steam separator passes to the condenser, whilst part of the steam passes through the superheater 3 and is used to roll and warm the turbine, the remainder being either used in the de-aerater 19, the high pressure feed water heater 20, the turbine seals 24, or passed to the condenser 13 through a desuperheater 22. In a modification (Fig. 2) a two part superheater is utilized and throttling valves (23) are incorporated between the evaporator surface and the first part of the superheater, whereby the former may be brought up to full operating pressure whilst the turbine may be supplied with low pressure high enthalpy steam according to its requirements during start-up.