GB1143478A - A once-through vapor generator - Google Patents

Abstract

1,143,478. Once through vapour generators. COMBUSTION ENG. Inc. 23 Aug., 1966 [16 Sept., 1965], No. 37816/66. Heading F4A. A once through vapour generator operates with water recirculation through the radiant heat-absorbing sections at low loads, to prevent overheating of the tubes. At full load, feedwater from economizer 11 is conveyed through mixing vessel 14 and downcomer 15 by pump 17 to the vertical wall tubes 19 lining the furnace chamber 3. From wall tube outlet headers 20, the water then passes to wall tubes lining the rear gas pass 5, and thence to platen inlet header 28. The majority of the fluid flow then passes through the platens on its way to header 33 through support tubes 32, the remainder passing directly to header 33 through further support tubes 34. From header 33 the flow passes through throttle valve 37 to low temperature primary superheater 38, and then through high temperature primary superheater 39 on its way to a high pressure turbine (not shown). Returning fluid from the turbine is reheated in low temperature reheater 43 and then high temperature reheater 46 before passing to further turbine stages (not shown). At low loads some fluid is recirculated from header 33 through line 48, mixing vessel 14, the furnace wall tubes 19 and the platen tubes 29 to prevent these tubes from overheating. The tubes 32 support the platen tubes 29 and also those final reheater and final superheater tubes 46, 39 that are in the same plane as the platen tubes, whilst other fluid reheater and superheater tubes are supported by the support tubes 34. The tubes 32 and 34 are in turn supported by the roof seals 53.