GB627837A - Improvements in or relating to steam power plants provided with feed water preheaters and feed water accumulators - Google Patents

Abstract

627,837. Feedwater heating systems. SULZER FRERES SOC. ANON. Feb. 25, 1946, No. 5806. Convention date, March 23, 1945. '[Class 64(i)] [Also in Groups XXVI and XXIX] In a steam power plant with a feedwater accumulator and a multi-stage feedwater heating system in which the feedwater, after being heated at one stage by steam in quantity automatically dependent on a factor in the working condition of the accumulator is heated in the last stage to the accumulator temperature by steam in quantity automatically dependent on a working factor in the plant, the quantity of steam given up to the prime mover, e.g. a turbine, is automatically altered when, and in the same sense as, the quantity of steam used in the preheating of the last stage is altered. In the form shown, in which steam from a boiler 1, after driving a multi-stage turbine 4, is condensed in a condenser 8, the condensate is passed by a pump 9 either to the bottom of a feedwater accumulator 11 without re-heating or, by means of a pump 12, to a cascade 16 in the steam space 17 at the top of the accumulator, through heat exchangers 13, 13a, which are heated by tapped steam from the turbine. Fresh steam supplied from the pipe 2 to the steam space 17 is condensed by the cascade of water and heats it to its final temperature. The supply of fresh steam to the accumulator and of tapped steam to the heat exchanger 13a are controlled by valves 21, 24 which are operated by servomotor systems 32, 34 and 40, 41 responsive to steam pressures respectively in the fresh steam pipe 2 and in the pipe 23 supplying the exchanger 13a. The flow of water through the heat exchangers 13, 13a is controlled by a servo-motor system 43, 45 responsive to the pressure in the steam space 17. Changes in this flow will result in changes in the steam pressure in the pipes 23, 26, 27 and consequently affect the operation of the valve 24 and the supply of steam to the exchanger 13a. If the steam pressure in the space 17 rises sufficiently, the valve 15 is opened wide enough for the pump 12 to take the unheated water from the bottom of the accumulator and pass it through the heat exchangers, so that the amount of heated water in the accumulator increases. A pipe 30 containing a safety valve 31 connects the steam space 17 to the condenser 8. A valve 3 controlling the steam supply to the turbine 4 is operated by a servo-motor system 35, 37, 38 controlled by the governor 6. The valves 3, 21 are linked by levers, so that opening and closing of the valve 21 results in opening and closing of the valve 3 in a predetermined ratio, but not vice versa. The pumps 12 and valve 15 may be replaced by a three-way or other valve controlled by the servo-motor system 43, 45. The valve 24 may also be subject to control by the governor 6, to meet a sudden demand for steam, and the valve 3 to a regulator which prevents the boiler pressure from falling too low.