US2884760A - Steam power plant - Google Patents

Description

- Filed Jan. 25, 1954 May 5, 1959 A.BUR1 2,884,760

STEAM POWER PLANT 4 Sheets-Sheet 1 25 Spain 1 1 CoMTQO -LIO VALVE INVENTOR.. ALFRED BURL 7 ATTOR/VEK May 5, 1959 Filed Jan. 25,

A. BURl STEAM POWER PLANT 4 Sheets-Sheet INVENTOR. ALFRED BURL fflf/dfb,

ATTOIFNEK May 5, 1959 A. BURI 2,884,760

' STEAM POWER PLANT Filed Jan. 25, 1954 4 Sheets-Sheet a INVENTOR.

I ALFRED BUR].

ATTO NEK May 5, 1959 A. BUR] 2,884,760

STEAM POWER PLANT Filed Jan. 25, 1954 i 4 Sheets-Sheet 4 v TT INVENTOR.

ALF'EED BUEI.

A TT'ORN E Y.

United States Patent STEAM POWER PLANT Alfred Buri, Winterthur, Switzerland, assignor to Sulzer Freres, Socit Anonyme, Winterthur, Switzerland, a corporation of Switzerland 3 Application January 25, 1954, Serial No. 405,697

Claims priority, application Switzerland January 27, 1953 1 Claim. (Cl. 60-73) The invention relates to a steam power plant having a resuperheater, usually called a reheater, heated by combustion gases and arranged between the high pressure part and the low pressure part of a turbine plant.

It is an object of the invention to provide a steam power plant in which, depending on the operating conditions and control actions, at least an adjustable portion of the generated steam is cooled and conducted through a reheater preferably into the condenser, bypassing the high pressure turbine. It is of advantage to mix the by-passed portion of the steam after it has been cooled, with the steam which produced power in the high pressure part of the turbine plant, and to conduct it into the reheater and to withdraw from the steam leaving the reheater the same amount by weight, which has by-passed the high pressure turbine, and to conduct it, for example, into the condenser. The portion conducted into the condenser is preferably cooled before it reaches the condenser.

The system according to the invention includes an overflow valve which adjusts the weight of the steam which by-passes the high pressure turbine part and is conducted through the reheater, and a regulating valve which adjusts the amount of steam by-passing the low pressure turbine and conducted, for example, into the condenser, to be the same amount, by weight, as the amount of steam which by-passes the high pressure turbine. The regulating valve is preferably actuated in accordance with the ratio between the pressure in the high pressure turbine housing and the pressure in the intermediate superheater. The regulating valve may also be operated according to the ratio between the amount of the steam passing through the high pressure part of the turbine plant and the amount of the steam by-passing this part of the turbine plant. It is of advantage to use the control mechanism of the steam admission valve of the high pressure turbine for controlling the regulating valve. The pressure of the steam at the outlet of the reheater may also be used for adjusting the regulating valve. A cooler arranged in the by-pass conduit between the regulating valve and the condenser may be of advantage.

With the arrangements according to the invention steam can be passed through the reheater so that the latter is cooled while the plant is started and at other abnormal operating conditions, for example, when the safety valve is closed, or when the turbine is disconnected from the system. The temperature regulation of the first superheater and of the reheater remains in operation also at abnormal operating conditions of the plant, and the steam generator as well as the turbine are also protected against harmful temperature variations.

The novel features which are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself however and additional objects and advantages thereof will best be understood from the following description of the embodiments thereof when read in connection with the accompanying drawing in which ice Fig. 1 is a diagrammatic layout of a plant according to the invention, parts of the plant being shown in section;

Fig. 2 is a large scale sectional view of a detail of the plant according to Fig. 1;

Fig. 3 is a sectional view of a modification of the detail shown in Fig. 2;

Fig. 4 is a diagrammatic layout of a plant, as shown in Fig. 1, adapted to be manually operated;

Fig. 5 is a large scale sectional view of a detail of the plant, shown in Fig. 4;

Fig. 6 is a diagrammatic illustration of a modified plant according to the invention;

Fig. 7 is a diagrammatic illustration of a further modification of the system according to the invention.

The same numerals designate the same parts in all figures.

Referring more particularly to Fig. 1 of the drawing, numeral 1 designates a steam generator, a one tube steam generator being illustrated. The feed water is supplied by means of a pump 2, preferably through a conven tional feed water heater, not shown. The steam is superheated in a superheater 3 and conducted through a steam main 4 and a valve 5 to the turbine plant. At the superheater outlet a by-pass conduit 6 is connected, conducting steam through an overflow valve 7 through a starting cooler 8 to a reheater 9 which is heated by combustion gases of the steam generator 1. A one-shaft turbine plant is shown, comprising a high pressure part 10, a medium pressure part 11, and a double low pressure part 12, the turbine plant driving, for example, an electric generator 13. The intermediate superheater or reheater 9 is heated by the combustion gases of the steam generator and reheats the steam flowing from the high pressure turbine 10 to the medium pressure turbine 11. The steam flows from the latter to the low pressure turbine 12 and therefrom to a condenser 14. Whereas the shafts of the high pressure and medium pressure turbines are interconnected, the low pressure turbine as Well as the electric generator are connected by means of axially movable clutches 15.

A conduit 16 branches from the outlet conduit of the reheater 9 and conducts steam through a regulating valve 17 into a cooler 18. The conduit 16 by-passes the medium pressure and low pressure turbines and conducts the steam to the condenser 14. The steam bypassing the high pressure turbine through the conduit 6 is cooled in the cooler 8 by means of cooling water taken from the feed water conduit through a valve 19, to a temperature which is suitable for the reheater 9, the separated water being conducted through a steam separator 20 and a conduit 21 to the cooler 18 and therefrom by way of a steam separator 20' and a conduit 21' to the condenser 14. A condensate pump 22 moves the condensate from the condenser 14 to the feed pump 2 through a conduit 23. The amount of cooling water needed by the cooler 18 is diverted from the conduit 23 and controlled by a valve 24, the diverted water and the steam being returned to the condenser through the conduits 21' and 16. At the connection of the steam main 4 with the high pressure turbine a conventional stop throttle valve 26 which is closed by a conventional speed governor 36 upon excessive turbine shaft speeds is provided ahead of a speed controlled valve 25, an additional conventional stop throttle valve 27, also responsive to the speed governor 36, being provided at the inlet of the medium pressure turbine. There are always a plurality of conventional speed controlled valves 25, one valve for each admission nozzle group, only one valve being shown to simplify the drawing. Numeral 37 designates a conventional control device for controlling the flow of an actuating fluid to the conventional servomotors of the valves 26 and 27, in accordance with the speed of the turbine 3 shaft which speed is measured by the governor 36. Valve 26 is closed only if the speed of the turbine shaft increases too much.

When the steam generator is started, at first amixture of steam and water is produced, whereupon the gradually increasing steam portion is gradually superheated at the end of the steam generator until the steam generator control begins to operate. The overflow valve 7 maintains the boiler pressure. When live steam of normal pressure and the desired temperature is available, the turbine plant can be started. Heating up is performed gradually without sudden temperature variations. The duration of the heating up stages may be extended without blowing the safety valves.

Depending on operating and regulating conditions,the generated steam is either conducted through the high pressure turbine or through the by-pass conduit 6 and through the cooler 8 to the reheater 9 for cooling and protecting the latter from the heat of the combustion gases. The steam emerging'from the reheater 9 is conducted either throughthe medium and low pressure turbines or through the regulating valve 17 to the condenser 14. If the steam flows through the by-pass conduit 6, it is important that undesired axial thrust be avoided in the high pressure turbine While the overflow valve is operating and that undesired load and speed variations or pressure conditions are prevented. For this :reason itis of advantage to mix the by-passed portion of the steam, after cooling, with the steam which has produced power in the high pressure turbine and to conduct it into the reheater, and to divert from the steam leaving the reheater such an amount of steam, by weight, and to conduct it to the condenser, as corresponds to the weight of the by-passed steam. The diverted steam portion is preferably cooled before it enters the condenser.

In order to assure faultless operation of the whole plant particularly during starting, an overflow valve and a regulating valve are provided, the former adjusting the amount of steam by-passing the high pressure turbine and being conducted into the reheater, and the latter adjusting the weight of the steam by-passing the low pressure plant and being conducted into the condenser. The regulating valve 17 provided after the reheater is constructed as a pressure maintaining valve for the resuperheater, the pressure being adjusted, for example according to the ratio between the steam pressure in the high pressure turbine casing and in the reheater.

Fig. 2 diagrammatically illustrates a device for operating the regulating valve 17 and the condensate valve 24. The valve 17 is interposed in the conduit 16 which is branched from the reheater outlet conduit and conducts steam through the cooler 18 to the condenser 14 and is actuated by a servomotor 28. The latter comprises a spring loaded piston 28 which is actuated by the pressure of the oil supplied through a conduit 29 and a conduit 29. The pressure of the oil is controlled by a device 35) receiving the oil through an orifice 31. The device 319 comprises a bellows system 32 controlling the opening of a valve 32'. The system 32 includes a plate 32 on the sides of which act different pressures. The ratio of the pressures acting on the plate 32 is determined, for example, by the pressure in the reheater 9 which is connected with the bellows on the upper side of the plate by a conduit 33 and by the pressure in the high pressure turbine casing which is connected with the device 30 by means of a conduit 34. The ratio of the pressures actuating the valve 32 is predetermined by the diameters of the upper and lower bellows. Valve 24 and its actuating mechanism is similarly constructed as valve 17. The piston 24 of the valve 24 is actuated by pressure oil supplied through conduit 29, controlled by means of the device 30, and conducted to the piston 24' through a conduit 29".

Instead of providing two bellows having different diameters acting on a common plate, two separate bellows 41 and 42 may be arranged acting on a balance beam 39 swinging on a stationary fulcrum 40, as shown in Fig. 3. The valve 32 is connected with one arm of the beam 39. This arm is loaded by a spring 43' whose pressure can be adjusted by manipulation of an adjusting screw 43.

If the reheater pressure is excessive, for example, 'because the overflow valve 7 has been opened, the valve 32 is opened and pressure oil escapes through the conduit 35. This reduces the pressure acting on the piston 28' which is moved to the left by the spring 28" so that the regulating valve 17 is opened, admitting steam through the conduit 16 to the condenser 14, which steam bypasses the medium and low pressure turbines until the desired equilibrium between the steam passing through the turbine and by-passing the turbine is obtained. If the overflow valve 7 is closed, the valve 32 is closed effecting closing of the regulating valve 17.

To maintain the desired ratio between the weight of the steam flowing through the turbine plant and the weight of the steam by-passing the turbine plant, the device 30 actuating the regulating valve 17 may be operated in many different Ways.

The device 30 for actuating the regulating valve 17 may be so adjusted that the regulating valve remains closed at normal pressure conditions and may be opened only at an undesired increase of the pressure in the reheater.

The system according to the invention can also be used in steam power plants including forced flow steam generators, in which the steam is twice reheated and which operate above the critical pressure of the steam and at very high superheater and live steam temperatures, for example 600 C. Instead of one-shaft turbine plants, multishaft plants may be used. The shaft of the high pressure turbine may be connected, for example, with the shaft of the low pressure turbine by means of a reduction gear. The high pressure turbine part and the low pressure turbine part may each drive an individual electric generator, and both parts may be electrically connected.

In a steam power plant according to the invention, the steam by-passing the turbine plant may be condensed in a condenser which is independent of the condenser of the turbine plant, or it may be blown into the atmosphere, if loss of condensate does not matter.

The method according to the invention may also be performed by hand in which case the plant according to Fig. 1 may be organized as shown in Fig. 4. The conduits 33 and 34 of the plant according to Fig. 1 are replaced by a conduit 45 which connects the reheater 9 by way of a bypass 16 with the manually adjustable regulating device 38, which is of the type shown in Fig. 5 and actuates the regulating valve 17 and the cooling water control valve 24. The speed governor 36 controls the conventional high pressure turbine admission valves 25 and the conventional safety stop valve 27 of the medium pressure turbine 11 in the conventional manner. The operator manipulates the device 38 according to the readings on steam flow meters 46 to 49. When starting the plant the valve 7 will be open and the valve 5 is closed. The steam flowing into the reheater 9 through the bypass 6 (flow meter 48) must be in proportion to the steam flowing through the bypass 16 (flow meter 49) into the condenser 14. If the amounts of steam flowing through the bypasses 6 and 16 are out of proportion, the operator will manipulate the adjustment 44 which controls the opening of the regulating valve 17 and of the cooling water valve 24 until the flow meters 48 and 49 show the same amounts of steam. When the temperature of the steam at the outlet of the steam generator 1 reaches the desired value, the valve 5 is partly opened so that the turbines can be started. The steam consumption of the turbines is controlled by conventional governors 36, control valves 25, and safety stop valves 26 and 27 in the conventional manner. The amount of steam flowing through conduit 4 to the high pressure turbine (flow meter 46) should conform with the amount of steam flowing to the low pressure turbines (flow meter 47) and should be greater if steam is bled from the high pressure turbine and the operator will control the device 38 accordingly. Both operating methods will be suitably combined so long as the valves 7 and 5 are only partly open. If during normal operation the high pressure turbine consumes less steam than is produced, the valves 17 and 24 will be so operated that the amount of steam entering the reheater 9 by way of cooler 8 (flow meter 48) equals the amount of steam by-passing the low pressure turbine (flow meter 49).

Fig. 5 illustrates a modification of the device 30 of the system according to Fig. 2. The valve 50- which controls the oil pressure actuating the regulating valve 17 and also the condensate valve 24 is opened by the pressure in the bellows 51 which may be the pressure in the reheater 9. A spring 52 tends to close the valve 50. The pressure of the spring 52 can be changed by manipulating an adjustment screw 44. Actuation of the regulating valve 17 depends on the ratio of the pressure inside the bellows 51 and of the pressure of the spring 52 which is manually adjusted.

Fig. 6 illustrates the power plant shown in Fig. 4 equipped with a flow meter 50 for measuring the amount of steam flowing to the high pressure turbine, and with a flow meter 58 for measuring the amount of steam bypassing the high pressure turbine. The flow meters 50 and 58 actuate conventional diaphragm devices 52 and 53, respectively, which actuate a lever 54 whose movements control a conventional servomotor 55 for operating the regulation valve 17. The device diagrammatical- 1y illustrated in Fig. 6 makes the operation of the valve 17 responsive to the ratio of the amount of steam pass- 6 ing through the high pressure turbine and of the amount of steam by-passing the high pressure turbine.

Fig. 7 illustrates the power plant shown in Fig. 4 equipped with a conventional control connection 56 connecting the speed governor 36 for the high pressure turbine 10 with a conventional servomotor 57 for operating the valve 17 connected thereto in accordance with the steam admission to the high pressure turbine. The device 36, 56, 57 opens the valve 17 when the steam admission to the turbine 10 is reduced, and vice versa.

What is claimed is:

A steam power plant comprising a steam generator, a high pressure turbine connected with said generator for receiving live steam from said generator, a combustion gas heated reheater connected with said high pressure turbine for normally receiving exhaust steam from said high pressure turbine, a low pressure turbine connected with said reheater for normally receiving resuperheated steam from said reheater, a condenser connected with said low pressure turbine for receiving steam from said low pressure turbine, a first conduit by-passing said high pressure turbine for conducting live steam to said reheater, an overflow valve in said conduit, a second conduit by-passing said low pressure turbine for conducting steam from said reheater to said condenser, a regulating valve in said second conduit, and actuating means for said regulating valve, said actuating means being responsive to the ratio of the steam pressures in said high pressure turbine and in said reheater.

References Cited in the file of this patent UNITED STATES PATENTS 2,271,886 Juzi Feb. 3, 1942 2,747,373 Eggenberger et a1. May 29, 1956 FOREIGN PATENTS 416,091 Great Britain Sept. 10, 1934

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