EP1502010B1 - Steam turbine - Google Patents

Description

Technical area

The invention relates to a steam turbine and in particular a valve arrangement for the live steam supply to the steam turbine.

State of the art

Steam turbines are known in which the fresh steam supply is regulated by nozzle control by means of a control stage, also called a first turbine stage. Such a control stage has, for example, differently sized admission sectors, to which the live steam is supplied in each case via a live steam inlet with a plurality of control valves. As a safety measure, the control valves are preceded by a quick-closing valve. Such an arrangement is described for example in the sales documentation of the ABB Power Generation, Description no. HTGD N12 018 discloses.
These steam turbines are typically operated at a live steam pressure, which is set by the operating parameters of the steam generator for all operating loads of the steam turbine. Through various settings of the three or four control valves, the steam turbine can be operated at a plurality of partial load points and also within these partial load points associated load ranges. For this purpose, the sequentially operable control valves are either closed or fully or regulated opened.

Other known steam turbines are operated without control stage. These typically have one or two live steam inlets, each with a quick-action valve and a downstream control valve. Such steam turbines are described, for example, in the sales documentation of ABB Power Generation, Description. HTGD 666 159 and a valve arrangement arranged therein for the regulation of the live steam supply in the same sales documentation, GMDT N06 014. The live steam pressure may be variable in these steam turbines, such as in steam turbine plants for sliding pressure operation or in steam turbine plants whose cycle is combined with a gas turbine plant.
However, in newer steam turbine plants, the live steam pressure can also be set at a single pressure level for all operating loads.

The valves in the steam turbine plants mentioned are preferably designed so that valve vibrations due to an increased load are kept within limits and the longest possible damage-free service life of the valve is granted.

In the steam turbines without control stage and in particular those that are operated at fixed live steam pressure, the valves must be in always throttled operation to allow safe partial load operation of the steam turbine. As a result, the valves are exposed to an increased load compared to the steam turbine with control stage. For steam turbines without a control stage, the pressure is reduced exclusively via the valves, while in steam turbines with control stage, the pressure is reduced via the valve and the upstream nozzles. The quick-acting valves ensure safety for the live steam supply, but can not assume a throttling function. Operating a steam turbine at fixed pressure may result in increased loads and critical pressure ratios in the control valves, causing correspondingly increased valve vibration and increased damage risk. This is particularly the case with steam turbines without control stage and throttle operation in partial load operation of the case.

JP 61126302 discloses two series-connected butterfly valves (English: butterfly valves) with a vapor sieve arranged between them. A housing for the steam strainer is assembled with separate housings for the two flaps. The disclosed flaps are typically suitable for the control of steam flows in the low pressure range, ie not for the live steam supply.

FR 2206438 discloses a method of controlling the operation of a steam turbine by means of a series of steam inlet valves, including throttle inlet valves (TV1-TV4) and regulator valves (GV1-GV8).

EP 0 361 835 discloses a system for monitoring the operating state of a throttle valve connected in series with a regulator valve.

Presentation of the invention

In view of these disadvantages of the known valve arrangements for the live steam supply, it is the object of the present invention to provide a valve arrangement for the control of live steam supply in a steam turbine, which have a reduced risk of damage, especially in the reduction of higher pressures.

This object is achieved by a valve arrangement according to claim 1.

A steam turbine has a valve arrangement for regulating the live steam supply, which consists of two control valves which are connected in series. According to the invention, the two control valves are each designed as unloaded single-seat valves with a pre-stroke or unloaded single-seat valves without a pre-stroke of the type of a tubular valve. In addition, the two control valves (6, 7) are arranged in a single housing.

This embodiment is particularly suitable for controlling the steam supply, ie steam in higher pressure ranges, and also has a reduced risk of damage when reducing the high pressures.

The inventive valve arrangement allows for partial load operation, a gradual reduction of the pressure loss across the two individual control valves, that is, the converted energy during throttle operation is distributed to the two or more control valves. The load of a single control valve is thereby greatly reduced in comparison to a valve arrangement with quick-closing valve and only one control valve. The risk of valve vibration and consequent possible valve damage is thereby reduced. The safety function of a quick-acting valve can be taken over by the first control valve in the arrangement according to the invention, so that the safety afforded by this valve arrangement is not reduced in comparison to the prior art.

The valve arrangement according to the invention can be applied to steam turbines both with and without control stage. In steam turbines without control stage, it reduces in particular the relatively high loads of the control valves there. Furthermore, it is suitable for steam turbines in fixed pressure operation as well as in operation with variable live steam pressure. Again, the valve arrangement according to the invention is particularly effective for steam turbines without a control stage and especially for those in the fixed pressure mode, the reduction of load-related valve vibrations.

The valve arrangement has the advantage that the problem of potential valve vibrations is achieved in particular in steam turbines without control stage and at fixed pressure operation by a simple arrangement of a single valve type and without loss of security. Next, it allows the advantage of known control valves and actuators can be used. For all control or control valves preferably the same drive are used.

There follow more detailed explanations of the inventions with reference to the figures.

Brief description of the figures

• Figur 1 ein Schema einer Dampfturbinenanlage, in der die erfindungsgemässe Ventilanordnung zur Regelung der Frischdampfzufuhr eingesetzt wird,
• Figur 2 eine Ventilanordnung gemäss der Erfindung mit zwei in Serie geschalteten Regelventilen vom Typs eines Rohrventils in einer Eckventilanordnung,
• Figur 3 eine Ventilanordnung gemäss der Erfindung mit zwei in Serie geschalteten Regelventilen vom Typ eines Vorhubventils in einer Eckventilanordnung.

Show it

• FIG. 1 shows a diagram of a steam turbine plant in which the valve arrangement according to the invention is used for regulating the supply of live steam,
• 2 shows a valve arrangement according to the invention with two series-connected control valves of the type of a pipe valve in an angle valve arrangement,
• Figure 3 shows a valve assembly according to the invention with two series-connected control valves of the type of Vorhubventils in a Eckventilanordnung.

Embodiment of the invention

1 shows schematically a steam turbine plant with a steam generator 1, which is connected via a live steam supply line 2 to a steam turbine 3. The steam turbine 3 is coupled to a generator G. The steam which has been expanded in the turbine is supplied to a condenser 4, condensate accumulating there being fed back to the water-steam circuit of the system.

The supply line 2 has a valve arrangement 5 for regulating the live steam pressure according to a predetermined operating load. The valve arrangement has here in the flow direction a first control valve 6 and a second control valve 7, which are connected to each other in series.

The control valves 6 and 7 each have an actuator 6a and 7a, which are connected to a control or regulating device 8. By the control device, the two control valves can be placed in a full closed position, a full open position or any partial open position. In particular, the first control valve 6 can also take over the function of a quick-acting valve.

The live steam generated in the steam generator 1 has on entry into the valve assembly 5 a live steam pressure P _D1 , which is there gradually reduced via the intermediate pressure P _Z to a vapor pressure P _D2 , which corresponds to a full operating load or a predetermined partial load.

The actuators 6a and 7a may be formed, for example, as a hydraulic drive with electro-hydraulic converter. Incoming electrical control signals are then converted into corresponding hydraulic currents, the corresponding Setting movements on the throttle bodies or shut-off valves of the control valves 6 and 7 generate.

Figure 2 shows a first possible embodiment of the inventive valve assembly, in which the control valves are designed as pipe valves. 2, the two control valves 6 and 7 can be combined in a common housing to form an assembly 20, whereby the installation effort in the installation of the live steam supply line 2 is simplified. As can be seen from FIG. 2, the two control valves 6 and 7 may expediently be configured identically with identical or similar components. In this way, on the one hand reduces the variety of parts and on the other hand can be reduced by higher quantities of the item price. In the two control valves 6 and 7, the valve seats or diffusers 22 may be the same or different, whereby the flow cross sections of the two valves are either the same or different.

Both control valves 6 and 7 are here designed as single-seat angle valves without advance stroke in the design of pipe valves, which are flowed transversely to the valve, while the outflow direction runs counter to the Ventilhubrichtung. In order to realize this flow and outflow with 90 ° deflection in both control valves 6 and 7, the two control valves 6 and 7 in the assembly 20 shown here are mutually rotated by 90 °. Accordingly, each control valve 6 includes a valve body 21 which cooperates in its closed position with a valve seat 22. In FIG. 2, one valve body half in the closed position of the valve body 21 and the other valve body half in the maximally open open position of the valve body 21 are shown for each valve body 21 with respect to a symmetry plane 23 perpendicular to the plane of the drawing.

FIG. 3 shows a further embodiment of the valve arrangement according to the invention. Here it is by unloaded single seat valves with advance in one Angle valve arrangement designed. Similar to Figure 2, the two control valves 6 and 7 are rotated by 90 ° to each other. Again, each control valve 6 includes a valve body 24 which cooperates in its closed position with a valve seat 25. For each valve body 24 on the plane of the plane of symmetry plane 26 which is a valve body half in the closed position of the valve body 24 and the other valve body half in the maximum open open position of the valve body 24 is shown.

The valve arrangement according to the invention is operated as follows:

On the input side of the first control valve 6 is set by the steam generator fresh steam pressure P _D1 . This pressure can be either a fixed predetermined pressure or a variable by predetermined measures in the boiler system predetermined pressure. The steam turbine 3 receives a working pressure P _D2 , which varies with the operating state of the steam turbine 3. With the aid of the valve arrangement 5, the live steam pressure P _{D1 present} on the input side is throttled to the actual working pressure P _D2 . According to the invention, this takes place in two stages, with the invention for the first stage comprising two different methods: According to the first method, the first control valve 6 throttles the live steam pressure P _D1 to an intermediate pressure P _Z , wherein this throttling is controlled. For this purpose, for example, the control valve 6 is set to a valve lift. The resulting intermediate pressure is then variable depending on the live steam pressure P _D1 . Suitably, this intermediate pressure P _{Z is} always slightly higher than the maximum required by the steam turbine 3 working pressure P _D2 .

According to the second method, the variable live steam pressure P _{D2 is} regulated by means of the control valve 6 to a load-dependent intermediate pressure P _Z. The actuation of the first control valve 6 is realized, for example, by a control circuit whose command variable is expediently formed by the load-dependent intermediate pressure P _Z. For this purpose, control deviations are determined by a desired-actual comparison of the values of the intermediate pressure P _Z and compensated by suitable control commands.

In both methods, the second control valve 7 now throttles from the intermediate pressure P _Z to the working pressure P _D2 , whereby this throttling takes place only regulated. A control loop for the actuation of the second control valve 7 contains as guide variables, for example, the power of the steam turbine or the rotational speed of the rotor of the machine. The working pressure P _D2 adjusts according to these reference variables. This means that control deviations, which are compensated for by a nominal / actual comparison of the values of the working pressure P _D2 or the reference values, according to which the working pressure adjusts, are compensated by suitable control commands.

Thus, the valve assembly 5 comes in the invention with two simple control circuits. By this construction, the effort for the control and / or control of the valve assembly 5 is reduced. Furthermore, at the same time results in increased reliability and reliability, which is due to the reduced stress on the valves. In addition, the two-stage throttling has the consequence that the maximum of the control valves 6 and 7 individually applied pressure differences are significantly smaller than the pressure difference between live steam pressure P _D1 and working pressure P _D2 , which causes the reduced stress on the control valves 6 and 7. In particular, vibrations, vibration excitations and noise developments can be reduced or avoided altogether.

LIST OF REFERENCE NUMBERS

1

steam generator

2

Live steam supply line

3

steam turbine

4

capacitor

5

valve assembly

6

First control valve

7

Second control valve

6a

actuator

7a

actuator

8th

regulator means

G

generator

20

module

21

valve body

22

valve seat

23

plane of symmetry

24

valve body

25

valve seat

26

plane of symmetry

Claims (5)

1. Steam turbine (3) with a valve arrangement (5) for controlling the supply of live steam into the steam turbine (3), the valve arrangement (5) having in the direction of flow of the live steam two control valves (6, 7), which are connected in series, characterized in that the two control valves (6, 7) are designed in each case as relieved single-seat valves with a work clearance stroke or relieved single-seat valves without pilot stroke of the type of a pipe valve, and the two control valves (6, 7) are arranged in a single housing.
2. Steam turbine according to Claim 1, characterized in that the steam turbine (3) is designed with or without a control stage, and the pressure (P_D1) of the live steam upstream of the valve arrangement (5) is set so as to be fixed or variable under all the operating loads of the steam turbine (3).
3. Steam turbine (3) according to one of the preceding claims, characterized in that the two control valves (6, 7) have in each case an actuating drive (6a, 7a) connected to a control apparatus (8) for open or closed-loop control of the actuating drives (6a, 7a).
4. Steam turbine according to one of the preceding Claims 1 to 3, characterized in that the flow cross-sections of the two control valves (6, 7) are identical.
5. Steam turbine according to one of the preceding Claims 1 to 3, characterized in that the flow cross-sections of the two control valves (6, 7) are different.

Images