GB820255A - Steam power plants employing forced-flow steam generators - Google Patents

Abstract

820,255. Feedwater supply and heating systems for steam boilers. SULZER FRERES S. A. Nov. 22, 1957 [Jan. 31, 1957]. No. 36412/57. Classes 64(1) and 123(2) In a steam power plant comprising a forced-flow boiler 1 of small storage capacity supplying a turbine set 2, transient fluctuations of steam temperature or pressure with consequent changes in turbine output are rapidly compensated by varying the bled steam flow from the turbine to feedwater heaters to make more or less steam available in the turbine to restore its output to the required value. In the arrangement shown, the turbine exhausts into a condenser 3 having a condensate trap 4 with a level regulator 5. A condensate pump 6 delivers water through preheaters 15, 15<SP>1</SP> respectively supplied with steam tapped from the turbine 2 through lines 23, 22 into a hot water accumulator tank 16, the preheating dome 24 of which is supplied with bled steam through a line 21. A feed pump 17 withdraws hot water from the tank 16 and delivers it through a high pressure preheater 18 supplied with bled steam through a line 20 to the boiler. A cold water acumulator tank 7 is shuntconnected to the pipe from the pump 6 to the first preheater 15 by inlet and outlet pipes 8, 9 respectively controlled by valves 11, 10, the outlet pipe 9 also including a pump 19. Between the point at which the pipe 9 enters the pipe from the pump 6 and the preheater 15 is a valve 13. The valves 10, 11, 13 are controlled by an output-dependent impulse transmitter 12. In operation, a part of the steam flowing through the turbine is tapped off through pipes 20... 23, the quantity being proportional to the flow of water through the preheaters 15, 15<SP>1</SP>, 24 and 18 so that if, for example, the steam pressure or temperature falls and the turbine output temporarily drops in consequence, the transmitter 12 throttles or closes the valve 13 whereby the water flow through the preheaters 15, 15<SP>1</SP> is reduced or stopped. The amount of steam tapped from the turbine drops proportionally correspondingly increasing the quantity of steam available to produce work in the turbine and thus increasing its output to the required value. As the valve 13 closes, the valve 11 is opened so that the tank 7 can take up the transient difference between the constant flow delivered by the pump 6 and the reduced flow through the valve 13. Stored hot water is delivered from the hot water accumulator 16 to the pump 17. In the event of a transient increase in steam temperature or pressure with consequent rise in turbine output, the transmitter 12 temporarily opens the valves 10, 13 and starts the pump 19 to deliver additional water to the preheaters 15, 15<SP>1</SP>. This results in an increased consumption of tapped steam and a consequential decrease in turbine output to the required value. Surplus water is stored in the tank 16. In a modification, the pipe 9 returns water to the trap 4, the pump 19 being omitted.