Patent GB-765140-A (GB)
Title: Steam power plants with intermediate reheaters
IPC: F01K7/22
Filed: 1955-01-24
Abstract: 765,140. Steam power plant. SULZER FRERES SOC. ANON. Jan. 24,1955 [Jan. 28, 1954], No. 2036/55. Classes 110 (3) and 122 (3). [Also in Group XIII] A method of regulating the intermediate reheating in a steam power plant having between two expansion stages an intermediate re-heater directly heated in the steam generator and a heat exchanger through one side of which passes at least some of the partially expanded steam and through the other side of which passes some not yet expanded steam, which comprises so controlling the operation of the heat exchanger that if the partially expanded steam is too cool additional heat is added to it in the heat exchanger and if too hot, heat is withdrawn therein. Feed water from the hot well 4 is fed by a pump 5 to the flue gas economizer 7 and boiler 8 where it is converted into steam. The steam is superheated in a first superheater 10 and then flows through one side of a heat exchanger 12 into a second superheater 14 from which it is led to a high-pressure turbine 16. After expansion in the turbine 16 the steam passes into the first part 18 of an intermediate reheater, then through the other side of the heat exchanger 12 into the second part 19 of the intermediate reheater from which it is led to a lowpressure turbine 21. The two parts 18, 19 of the intermediate reheater are directly heated in the furnace of the steam generator. Feed water is led through a pipe 24 to pipes 25, 26 controlled by valves 27, 29 which inject water into the not yet expanded steam before and after the heat exchanger 12. The valve 27 is automatically controlled by a regulator 28 in response to variations of temperature of the partially expanded steam leaving the heat exchanger 12. The valve 29 is automatically controlled by regulators 30, 31 responsive to the temperatures before and after the second superheater 14. A by-pass pipe 32 containing a throttle device 33 is arranged to pass some of the not expanded steam round the heat exchanger 12. The throttle device 33 can be a simple orifice diaphragm or a manually or automatically adjustable valve. A by-pass, including a throttle valve, around the other side of the heat exchanger 12 may also be provided. The control of the valve 27 is such that when the heat given to the partially expanded steam in the intermediate reheater 18, 19 is sufficient to maintain the desired reheat temperature, sufficient water is injected through the pipe 25 that no heat transfer takes place in the heat exchanger 12. When the heat supply in the intermediate reheater is insufficient, the amount of water injected is reduced and heat is transferred from the not yet expanded steam to the partially expanded steam. When the heat supply is excessive, the amount of water injected is increased and heat is transferred from the partially expanded steam to the not yet expanded steam. The heat exchanger 12 may be arranged before or after a one-part intermediate reheater. When there is more than one stage of intermediate reheating, it is advantageous to connect the sides of the heat exchangers 12 through which the not yet expanded steam passes in parallel and to provide an individual water injector for each. Alternatively, the steam temperature in only one of the reheaters could be controlled as described and the others regulated in some other way.