GB877706A - Steam generating plants - Google Patents

Abstract

877,706. Steam raising in boilers; superheaters. SULZER FRERES S. A. July 8, 1960 [July 23, 1959], No. 23995/60. Classes 123(2) and 123(3) The reheaters 26, 27 of a unit steam generating plant are cooled during starting-up, standby or shutting-down periods when the turbine is supplied with a small volume of steam by a flow of steam which is withdrawn through pipes 3, 6, 7, 8 from between the superheating sections 1, 2, 9 according to the local temperature in these sections. The flow through the pipe 3 branching from between sections 1 and 2 is controlled by a valve 13 which, during starting-up, is opened when the temperature at a pick-off 20 reaches a certain value. A steam-water mixture or steam flows through a pipe 5 into a separator 40 whence steam flows through a pipe 28 into the reheater 26. A separator by-pass 4 is provided so that wet steam can be admitted directly into the reheater. When the temperature increases further steam may flow in parallel through the reheaters, a pick off 21 responding to the temperature increase opening valves 10, 11 respectively disposed in pipes 6, 7 which branch off between the sections 2 and 9. The increased pressure in pipe 3 is detected by a pick-off 23 which closes the valve 13. A further increase in temperature causes the pick-off 21 to open a valve 12 in the pipe 8 which also branches off between the sections 2 and 9 and steam then flows through the water separator into the pipe 28 and thence in series through the reheaters and an interposed valve 30. The increased pressure in the pipe 28 causes a pick-off 22 to close the valves 10, 11. Water for additional cooling may be injected thrugh pipes 35, 51. The cooling of the reheaters during standby operation and during the shutting- down period is carried out in a similar manner.