Improvements in or relating to steam boilers having a single stage reheater or multiple stage reheaters convectively heated by flue gas

摘要

772,566. Forced-flow and critical pressure steam boilers; superheaters. SIEMENSSCHUCKERTWERKE AKT.-GES. May 3, 1955 [May 3, 1954], No. 12848/55. Classes 123(2) and 123(3) A forced-flow, once through boiler operating at a pressure which may exceed the critical pressure has two parallel-connected tube systems comprising preheaters 3, 4 from which water flows to radiantly-heated evaporating and superheating sections 19, 20, steam from'these sections passing via coils 18, 17 respectively housed in reheat steam inlet headers 16, 15 to convection superheaters 7, 8. Steam from each superheater 7, 8 'enters a common collector 9 from which it passes to the turbine served by the unit through a pipe 10. Steam from the high pressure and the intermediate pressure stages of the turbine is returned to the headers 15, 16 respectively wherein it is partly reheated in indirect contact with the steam from the sections 19, 20, the reheating being completed in convection reheaters 13, 14. Reheat temperature for both stages is controlled by proportioning the gas flow through the reheaters by dampers 11, 12. The cooling of the steam from sections 19, 20 in the heat exchangers prevents overheating of the superheaters 7, 8. At the same time the preheating of the reheat steam allows high reheat temperature to be obtained using convection reheaters.