GB926949A - Regulation of forced-flow once-through steam generators - Google Patents

Abstract

926,949. Fluid-pressure servomotor control systems. SULZER FRERES S.A. Feb. 6, 1962 [Feb. 15, 1961], No. 4560/62. Class 135. A method of automatically regulating a forced-flow once-through steam generator which comprises influencing both the feed flow and the quantities of fuel and combustion air by a main signal dependent upon steam temperature sensed in the region of the final superheating and subjected to conversion with a PID characteristic, and by an auxiliary signal dependent upon a temperature of the working medium, sensed at a point upstream of that at which the main signal temperature is sensed, and subjected to conversion with a PD characteristic. In the first embodiment, Fig. 1, the forced-flow once-through steam generator comprises a water supply pipe 4, an economizer 1, a conversion zone 2, a superheater 3 and a furnace 8 having fuel and air supply pipes 9 and 10. A temperature detector 15 is located at the end of the superheater 3 and its signal is passed to PID units 17 and 18 connected respectively to addition points 21 and 22. A temperature detector 23 is located at the conversion zone 2 and its signal is passed to PD units 25, 26 connected to the addition points 21, 22. From the addition point 21 the signal is fed to the addition point 30 connected to the servomotor 6 of the feed water regulating valve 5. From the addition point 22 the signal is fed to an addition point 33 connected to servomotors 13, 14 which control fuel and air supply valves 11 and 12 respectively. A pressure-measuring element 36 transmits signals to PID units 38, 39 connected respectively to addition points 33 and 30. A measuring device 43 responds to the CO 2 content and is connected to the addition point 35. The PID units 38, 39 may receive a desired value signal W, a turbine output signal N, a fixed programme signal P or a main frequency signal f. The detecting elements 15, 23 and the PID, PD units 17, 25 are constructed as shown in Fig. 2. In another example, Fig. 3 (not shown), the output signals from the PID units 17, 18 form desired value signals for the units 25, 26 respectively. The addition point 35 is replaced by a controller and the pressure detector 36 by a flow detector. In another example, Fig. 4 (not shown), the steam from the superheater 3 is fed to a turbine driving an electric generator and the signal from the pressure detector 36 is transmitted to a PID unit which controls a turbine supply valve. A hand wheel or turbine speed-operated setting unit may be associated with the PID units. The superheater 3 may be divided into two stages between which is located a water or wet steam injection valve actuated by a two or three characteristics controller responsive to signal from a temperature detector after the superheater.