GB754994A - Removing salts deposits from forced flow, once through steam generators - Google Patents

Abstract

754,994. Forced flow and critical pressure steam boilers. SULZER FRERES SOC. ANON. Oct. 1, 1954 [Oct. 27, 1953], No. 28392/54. Class 123(2). A method of operating a forced flow once-through boiler generating steam at subcritical or supercritical pressure whereby the steam output is maintained during the periods when the conversion zone of the boiler is flushed out to free it from deposited salts comprises by-passing the working medium around the zone to another part of the generator wherein it is converted into steam whilst the flushing is taking place. In one form the generator comprises a pump 1 which feeds water through a preheater 2 into a heat exchanger 4 where conversion into steam takes place, the steam flowing through pipe 5 and 3-way valve 6 to a superheater 7 whence it is led back through pipe 9 to the heat exchanger to heat the incoming water to supercritical temperature. The partly cooled steam leaves the heat exchanger and flows through a pipe 10 to a final superheater 11. When flushing of the heat exchanger becomes necessary, the valve 6 is actuated to permit water to flow directly into the superheater 7 wherein it is evaporated, a valve 12 being opened to allow the steam to by-pass the heat exchanger. A valve 15 in a branch discharge pipe 14 is then opened and part of the heated water from preheater 2 flows through the heat exchanger to dissolve out and carry away the salts deposited therein. In a modification, provision is made for the introduction of a flushing medium from an external source and for an additional heat exchanger 4 connected so that either heat exchanger can be shut off for flushing whilst steam is being generated in the other.