GB770091A - Improvements in or relating to forced-flow once-through steam boilers and methods ofremoving salt therefrom - Google Patents

Abstract

770,091. Forced-flow steam boilers. SIEMENS-SCHUCKERTWERKE AKT.-GES. May 2, 1955 [April 30, 1954], No. 12726/55. Class 123(2) In a forced-flow, once-through steam boiler having a tube system divided into two parallel-connected, individually regulable portions comprising respectively feed valves 13, 13<SP>1</SP>, economizers 2, 2<SP>1</SP>, radiantly heated first stage evaporators 3, 3<SP>1</SP>, final evaporators 4, 4<SP>1</SP> and primary superheaters 5, 5<SP>1</SP>, and convection heated secondary superheaters 6, 6<SP>1</SP>, steam-water separators 8, 8<SP>1</SP> are inserted between evaporators 4, 4<SP>1</SP> and superheaters 5, 5<SP>1</SP> respectively, the separators being dry during normal operation. When it becomes necessary to flush salts from the evaporators 4, 4<SP>1</SP>, this is done, preferably during a period of light load operation. whilst maintaining the steam output by flushing the evaporators alternately, the feed valve 13, for example,. being opened to increase the water supply to the left-hand tube portion until wet steam containing 10 to 20 per cent of water enters the separator 8. The water dissolves salts from the evaporator 4 and is removed from the steam in the separator. Saturated steam passes forward into the superheaters 5, 6. Meanwhile the righthand tube portion may be operated to give a higher steam temperature at the outlet from the superheater 6<SP>1</SP> so that when mixed at 14 with the steam at reduced temperature from the superheater 6, steamat the correct temperature leaves the outlet pipe 7.