GB891136A - Steam power plants with intermediate reheating - Google Patents

Abstract

891,136. Steam turbine plant. SULZER FRERES S.A. Dec. 22, 1960 [Dec. 23, 1959], No. 44119/60. Class 110 (3). A steam turbine plant comprising an intermediate reheater between two stages and at least one secondary consumer has at least one tapped steam supply line to the secondary consumer from a main turbine of the plant and another tapped steam supply line to the secondary consumer from the intermediate reheater. Steam from a boiler 1 is led to a highpressure turbine cylinder 3 which discharges through an intermediate reheater 5 to the lowpressure turbine cylinder 6. From an intermediate header 7 steam passes through a line 10 containing a regulating valve 11 to an auxiliary turbine 8 driving a generator 9. A by-pass 12 fitted with a restrictor 13 is connected in parallel with the valve 11. A steam line 14 tapped from the low-pressure turbine 6 and fitted with non-return valves 15, 16 also leads to the auxiliary turbine 8. A preheater 18 is connected as another secondary consumer to a branch 17. A pressure measuring element 19 measures the steam flow into the auxiliary turbine 8. At normal load, steam for the auxiliary turbine 8 is taken from the lowpressure turbine 6. As the load on the main turbine decreases the steam pressure in the line 14 drops and the measuring element 19 adjusts the valve 11 so that steam flows from the intermediate superheater into the auxiliary turbine 8. The restriction 13 allows sufficient steam to flow through line 10 even when valve 11 is closed so as to prevent condensation when the valve 11 is opened. In a modification, an additional regulating valve is located in the line 14. In this arrangement a speed governor on the auxiliary turbine shaft first opens the additional regulating valve and when this valve is completely open, the valve 11 is opened and the additional regulating valve closed, if no non- return valve is provided in the line 14. In another modification, Fig. 4 (not shown), the auxiliary turbine drives a boiler feed pump and the regulating valves in the supply lines from a main turbine cylinder and the reheater are controlled by a speed governor driven by the auxiliary turbine. In a modification of this arrangement, Fig. 5 (not shown), a desired value signal from the feed water regulating system or load regulator is led to a regulator where it is compared with the actual speed of the auxiliary turbine. The regulator then transmits to a comparator unit a control signal corresponding to the desired value of the pressure of the steam supplied to the auxiliary turbine where it compared with the actual steam pressure and a regulating signal transmitted to one or other of the regulating valves in the bled steam supply lines.