GB1338068A - Steam power plant - Google Patents

Abstract

1338068 Steam generators SULZER BROS Ltd 18 Jan 1971 [19 Jan 1970] 2351/71 Heading F4A In a steam plant, heat is extracted from steam produced in the evaporator 8 to heat the feedwater, and upon occurrence of a peak load, the rate of heat extraction is temporarily reduced. A forced circulation plant has a feedwater vessel 1 from which the water is drawn by pump 2 and delivered through valve 48 to an economizer 3 leading to a mixing vessel 27 in parallel with a separator 39. The water is drawn through line 25 by circulation pump 26 and forced through the evaporator 8 heated by a burner 42. Steam passes through three-way valve 21<SP>1</SP> into the separator 39 and then through two-stage superheater 10 into live steam line 11 which feeds a turbine 12. Thic comprises two stages with an intermediate reheater 31. Exhaust steam from the turbine is condensed at 13 and delivered by pump 14 into the vessel 1. During normal operation some steam is fed from valve 21<SP>1</SP> through pipe 40 into the mixer 27 to heat the feedwater. Valve 21<SP>1</SP> is operated by an actuator 37 controlled by means 36 responsive to the live steam pressure measured by detector 33, or alternatively to the rate of flow. When peak load occurs the pressure falls and valve 21<SP>1</SP> reduces the steam supply to the mixer 27. Simultaneously the pressure detector 33 acts on controller 34 and load controller 35 to open valve 44 and increase the fuel supply to burner 42. The three-way valve 21<SP>1</SP>is also influenced by the flow of water to an injection line 29 which controls the degree of superheat. This flow is controlled by a valve 30 responsive to the live steam temperature. The flow of feedwater to the economizer 3 is controlled by the level in the separator 39 acting upon a sensor 46 which controls the ! valve 48. In another embodiment, Fig. 3 (not shown), the separator and mixer form a single unit (39) and the three-way valve (21<SP>11</SP>) is disposed between this separator and the economizer 3. This valve (21<SP>11</SP>) controls the quantity of feedwater sprayed into the separator and is itself controlled by the output of an electric generator (61) driven by the turbine. In a further embodiment, Fig. 1 (not shown), applied to a natural circulation steam plant, the three-way valve (21) is disposed between the economizer 3 and a steam/water drum (5, and controls the quantity of feedwater sprayed into the drum. The three-way valve is itself controlled in dependence upon the water level in the drum, the actual flow rate of feedwater and the flow rate of steam on the live steam line. The fuel supply is also increased at peak load.