GB1091831A - Means for heating district-heating water in power and district-heating plants - Google Patents

Abstract

1,091,831. Automatic control systems. STAL LAVAL TURBIN A. B. Feb.16, 1966 [Feb. 26, 1965], No.6773/66. Heading G3R. [Also in Divisions F1 and F4] In a steam turbine plant comprising a highpressure turbine (not shown) preceding a lowpressure turbine set comprising a contra-rotating radial-flow turbine 7 exhausting through pipes 16, 17 to axial-flow turbines 10, 11 and 12, 13, steam is bled through pipes 23, 25 to condensers 24, 26 where it is used to heat water which is passed through the condensers in series, the water being used for district heating. The steam supplied to the condenser 26 is at a higher pressure than that supplied to the condenser 24. To keep the hot water at a constant temperature, the amount of steam diverted to each condenser 24, is varied in accordance with the steam pressure in each condenser by adjustment of a respective interstage throttle valve 18 or 19. For this purpose, the pressure in condenser 24 is sensed by a sensor 29 and applied through a conductor 31 as an electric signal to a proportional link 33, where it is added to a signal from an adjustable potentiometer 35 representing the desired pressure and to a restoring signal transmitted through a conductor 37 from a position sensor (not shown) of an electrically controlled hydraulic servomotor 67 which actuates the valve 18. The resultant signal is transmitted from the proportional link 33 to the control magnet of the servomotor 67 via switches 58, 39, an amplifier and a conductor 41. A similar arrangement is provided for controlling the valve 19 associated with the condenser 26. If, when the valves 18, 19 are fully open, the temperature of the hot water is still too high, the supply of steam to the condenser 26 can be further reduced by a throttle valve 43 actuated by a servomotor 65 in accordance with the steam pressure in the condenser 26, the control circuit being similar to that for the servomotor 67. A similar arrangement may be provided for reducing the supply of steam to the condenser 24. If the hot water is too hot even when the valve 43 is closed, a by-pass 50 around the condenser 24 or a by-pass 51 around both condensers 24, 26 can be opened by respective throttle valves 52, 53 controlled by temperature sensors 54, 55. If the steam pressure upstream of valve 43 becomes excessive, a pressure governor 56 adjusts throttle valves 5, 6 at the inlet to the turbine 7. Instead of being controlled in accordance with the pressure in condenser 24, the servomotor 67 can be controlled by the servomotor 68 so that it maintains a positional difference relative to the latter. For this purpose switch 58 is operated to connect the servomotor 67 to a proportional link 57 which is connected via conductors 61, 62 to the position sensors of both servomotors and also to a potentiometer 60 for setting the desired positional difference.