GB1280234A - Improvements in and relating to forced flow steam generators with working fluid re-circulation - Google Patents

Abstract

1280234 Steam generators SULZER BROS Ltd 25 July 1968 [25 July 1968] 37583/69 Heading F4A In a forced flow steam generator which comprises a pre-heater for feedwater, on evaporator within a combustion chamber, a water separator connected to the evaporator outlet, and a pump to recirculate water from the separator to the evaporator at part load, there are provided means in which, at least in the tap load range of the generator, some of the steam leaving the evaporator is condensed on at least some of the pre-heated water, and means to deliver the condensed steam and feedwater to the evaporator. As shown feedwater is fed through a preheater 2 to a mixer 3. At temperatures equal to the saturated steam temperature at the evaporator outlet 7, a mixture of steam and water is fed to the water separator 8, the separated steam flowing to a superheater 11 and a turbine (not shown), and the separated water flowing through a non-return valve 14<SP>1</SP> to the mixer 3. A pump 4 recycles the separated water together with the pre-heated feedwater to the evaporator inlet 5. At temperatures above the saturated steam temperature at the evaporator outlet 7, part of the generated steam is fed to the mixer 3 via a by-pass line 12, non-return valve 14 and control valve 13, in which mixer it condenses on the pre-heated feedwater. The mixture is then recycled by pump 4 to the evaporator inlet 5. To improve mixing, the mixer 3 contains baffles in the form of perforated plates. Irrespective of the type of operation of the generator, a quantity of steam is continually fed from the evaporator outlet 7 to the mixer 3 to act as a barrier against return flow of water. The evaporator 6 is formed by parallel vertical tubes which line substantially the entire height of the combustion chamber. In another embodiment, Fig. 2 (not shown), the water separator and the mixer are combined to form a single unit. A control system, which comprises a temperaturesensitive element (23), controller (24), pressuresensitive element (25) and a transmitter (26), ensures that a distributer (21) which divides the flow of feedwater in two, is so adjusted that the temperature of the steam in line (22) remains between 10‹ and 20‹ C. below the saturated steam temperature.