GB753588A - A method and apparatus for reducing the temperature and pressure of superheated steam - Google Patents

Abstract

753,588. De-superheating steam. FAIRELY, T. Oct. 19, 1954 [Oct. 19, 1953], No. 28770/53. Class 55(2). [Also in Group XIII] Superheated steam is usefully disposed of during the starting up or closing down of a boiler, by passing it through a constricting orifice of fixed area and from thence through a pipe run of constantly increasing diameter, during which time it is sprayed with a cooling liquid, preferably water, the steam being eventually passed into immersion heaters in a liquid to be heated, preferably, feed water. The boiler 1 has the usual header drum 2, superheater 3, main stop valve 5 leading to turbine 6, and a leak-off valve 4 for withdrawal of the steam when the turbine is out of use, e.g., when starting up or closing down the boiler. Condensate from the turbine 6 is returned to the feed tanks 7. The leak-off steam is desuperheated by passing it through an orifice plate 21A into a pipe 21 having a greater section than the preceding pipe 4B, and in sequence through other orifice plates 21B, the pipes receiving the steam from the orifice plates becoming progressively of larger section. Each orifice plate consists of a disc 24 held between pipe sections 22, 23, a hard steel insert 25 being held in place by the flange 22A, the insert having a tapered bore 25A. Water is supplied to the space 24B around the insert from a pipe 26, so that the increased speed of the steam through the bore 25A draws the water through the passage 24C into the pipe 23 to mingle with, and cool, the steam, which, after its final passage through an orifice plate 21B and mixing with water, passes through pipes 21C to immersion heaters 27, as described in Specification 700,531, [Group XIII], in the feed-water tanks 7. The cooling water for the orifice plates and the heaters 27 is supplied either from tanks 29 which are replenished by the feed pump 8 and pipe 9A, or, by adjustment of the three-way valve 30, the high pressure supply may be taken from the pipe 9A through the pipes 9B, 26C. The steam from the pilot safety valve 4A is passed through the orifice plates &c. to the feed-water tanks. In a modification, a number of boilers have their superheaters connected through separate leak-off valves to a common orifice-plate line.