EP3219939A1 - Verfahren zum betreiben einer dampfturbine - Google Patents

Abstract

A method of operating a steam turbine (10), wherein the steam turbine (10) is supplied from a steam source (11) steam (12) having a relatively high vapor pressure (p1) for relaxation, and leaving the steam turbine (10) Abdampf (13), which has a relatively low Abdampfdruck (p2), a downstream process (14) is fed as process steam, wherein the actual Abdampfdruck (p2) of the steam turbine (10) leaving the exhaust steam (13) is detected by measurement, and wherein depending on the detected actual Abdampfdruck a steam turbine associated control valve (15) and / or an auxiliary control valve (17), in particular a steam turbine bypass (16) associated with a bypass valve (17) are controlled. Then, when the actual Abdampfdruck (p2) is less than a limit or reaches a limit, is used to control the actual Abdampfdrucks to a desired Abdampfdruck exclusively the auxiliary control valve (17), in particular the bypass valve (17) of the steam turbine bypass (16) , whereas the control valve (15) of the steam turbine (10) is driven to set a steam mass flow (M) through the steam turbine (10). (Fig. 1)

Description

The invention relates to a method for operating a steam turbine.

From practice it is known that a steam turbine is supplied from a steam source steam for relaxation, wherein energy obtained in the relaxation of the steam is converted into mechanical energy, and wherein the steam turbine leaving exhaust steam can be fed to a downstream process as process steam. Such process steam can be used, for example, in the papermaking or chemical industries. In known from practice processes for operating such steam turbine processes, when the Abdampfsdruck the Abdampfs drops too much below a fixed or static limit, a protective shutdown is performed for the steam turbine to avoid damage to the steam turbine, in particular blade damage to the steam turbine. Such a large decrease in the exhaust steam pressure can be present in the paper-making industry, for example, if there is a paper tear on the papermaking machine, as a result of which the assemblies of the papermaking machine which serve the paper web guide take off too much exhaust steam and the exhaust steam pressure thereby drops too much. This leads in practice to the protective shutdown of the steam turbine and thus the stoppage of the process in the papermaking industry to a standstill of the paper production process.

Although such a protective shutdown of the steam turbine is required in practice to avoid damage to the steam turbine, the protective shutdown is disadvantageous because, on the one hand, the downstream production process is interrupted, on the other hand, if necessary, no mechanical energy is available, the operation of the steam turbine is produced.

There is therefore a need for a method for operating a steam turbine, by means of which without the risk of steam turbine damage, in particular without the risk of blade damage to the steam turbine, a protective shutdown of the steam turbine can be avoided as much as possible.

On this basis, the present invention has the object to provide a novel method for operating a steam turbine. This object is achieved by a method according to claim 1. According to the invention, when the actual Abdampfdruck is less than a limit or reaches a limit, only the auxiliary control valve, in particular the bypass valve of the steam turbine bypass, controlled to control the actual Abdampfdrucks to the SollAbdampfdruck, whereas the control valve of the steam turbine is driven to a Adjust steam mass flow through the steam turbine. The limit, with the reaching or falling below the control valve of the steam turbine is used to adjust the steam mass flow through the steam turbine, has a defined distance to the Abdampfdruck, at which the protective shutdown of the steam turbine would take place. Upon reaching or falling below this limit, only the auxiliary control valve, in particular the bypass valve of the steam turbine bypass, used according to the invention for controlling the actual Abdampfdrucks to the desired Abdampfdruck. The control valve of the steam turbine then serves to adjust the steam mass flow, in particular the steam mass flow, through the steam turbine. In this way, a protective shutdown of the steam turbine can be avoided without the risk of damage to the steam turbine, in particular the risk of blade damage to the steam turbine.

According to an advantageous embodiment of the invention, when the actual Abdampfdruck is less than the limit or reaches the limit, to set the steam mass flow through the steam turbine depending on the detected actual Abdampfdruck determined a steam turbine internal target steam pressure and the control valve of the steam turbine so controlled that a detected in-steam turbine Actual vapor pressure corresponds to the steam turbine internal desired vapor pressure. Hereby, the steam mass flow through the steam turbine can be adjusted particularly advantageous with the aid of the control valve of the steam turbine. About the regulation of the steam turbine internal actual vapor pressure on the steam turbine internal desired vapor pressure of the steam mass flow is controlled indirectly by the steam turbine. Preferably, such a steam turbine internal actual vapor pressure for adjusting the steam mass flow is controlled by the steam turbine, which corresponds to a pressure of that stage of the steam turbine, the exhaust steam is fed to the downstream process as process steam.

Preferably, a maximum permissible steam mass flow is determined by the steam turbine depending on the detected actual Abdampfdruck, depending on the maximum allowable steam mass flow through the steam turbine, the steam turbine internal desired steam pressure is determined. This allows a particularly advantageous adjustment, in particular regulation, of the steam mass flow through the steam turbine.

Preferably, when the actual boil-off pressure is greater than the threshold value, both the control valve of the steam turbine and the auxiliary control valve, in particular the bypass valve of the steam turbine bypass, are controlled to control the actual boil-off pressure to the desired boil-off pressure. Then, if the actual Abdampfdruck is greater than the limit, there is no risk of damage to the steam turbine or a protective shutdown of the steam turbine, so then both the control valve of the steam turbine and the auxiliary control valve, in particular the bypass valve of the steam turbine bypass, to control the actual Abdampfdrucks be controlled to the desired Abdampfdruck to control the actual Abdampfdruck to the desired Abdampfdruck.

Fig. 1:

ein Blockschaltbild zur Verdeutlichung des erfindungsgemäßen Verfahrens zum Betreiben einer Dampfturbine; und

Fig. 2

ein Kennfeld zur weiteren Verdeutlichung des erfindungsgemäßen Verfahrens zum Betreiben einer Dampfturbine.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention are, without being limited thereto, explained in more detail with reference to the drawing. Showing:

Fig. 1:

a block diagram for illustrating the method according to the invention for operating a steam turbine; and

Fig. 2

a characteristic diagram for further clarification of the method according to the invention for operating a steam turbine.

Fig. 1 schematically shows a to be operated by means of the method according to the invention steam turbine 10, wherein the steam turbine 10 is supplied from a steam source 11 steam 12 for relaxation in the steam turbine 10. Relaxed exhaust steam 13, which leaves the steam turbine 10, is fed to a downstream process 14 as process steam.

The steam 12, which is supplied to the steam turbine 10 for relaxation, has a relatively high vapor pressure p1, which is detected by measurement, namely by means of a pressure sensor 24. The exhaust steam leaving the steam turbine 10 has a relatively low exhaust steam pressure p2, which also metrologically detected, again by means of a pressure sensor 25th

According to Fig. 1 are the metrologically detected actual pressures, namely the metrologically detected actual vapor pressure p1 of the steam to be relaxed 12 and the metrologically detected actual steam pressure p2 of the exhaust steam 13, a control device 19 can be fed. Then, when the actual steam pressure p1 of the steam 12 to be relaxed is too large, excess steam 12 can be diverted via a valve 18, in particular into the environment or to an (auxiliary) condenser.

According to Fig. 1 the steam turbine 10 is associated with a control valve 15 which is positioned upstream of the steam turbine 10.

Further shows Fig. 1 a steam turbine bypass 16, in which a serving as an auxiliary control valve bypass valve 17 is integrated. When the bypass valve 17 is closed all steam 12 is passed through the steam turbine 10. When the bypass valve 17 is open, however, steam 12 can be conducted past the steam turbine 10.

Then, when the actual boil-off pressure p2 of the exhaust steam 13 is greater than a threshold value and therefore there is no risk of damaging the steam turbine 10, the control device 19 for regulating the actual boil-off pressure p2 to a target Abdampfdruck both the control valve 15 of the steam turbine 10 and the bypass valve 17 of the steam turbine 16 bypassed. This is done in the sense of a cascaded control preferably such that the control valve 15 of the steam turbine 10 depending on a difference between the actual Abdampfdruck p2 and a first target Abdampfdruck and the bypass valve 17 depending on a difference between the actual Abdampfdruck p2 and a second Target Abdampfdruck be controlled, wherein the second target Abdampfdruck is smaller than the first target Abdampfdruck.

Then, on the other hand, if the actual exhaust steam pressure p2 becomes smaller than the limit value or reaches the limit value, ie if there would be a risk of damage to the steam turbine 10, only the bypass valve 17 will be used to control the actual exhaust steam pressure p2 to the desired exhaust steam pressure used by the steam turbine bypass 16 or driven by the control device 19. The control of the actual boil-off pressure p 2 to the desired Abdampfdruck is then no longer made via the control valve 15 of the steam turbine 10, but then the control valve 15 of the steam turbine 10 is used to set a steam mass flow M through the steam turbine 10.

For this purpose, when the actual boil-off pressure p2 is less than the limit value or reaches the limit value, the procedure is that of the control device 19 for controlling the steam mass flow M through the steam turbine 10 dependent From the detected actual exhaust steam pressure p2 first a maximum permissible steam mass flow is determined by the steam turbine 10, preferably map-dependent. Subsequently, depending on the maximum permissible steam mass flow, a desired steam pressure within the steam turbine is also determined by the control device 19 as a function of the characteristic map, depending on the characteristic. The control valve 15 of the steam turbine 10 is then controlled by the control device 19 so that a detected by means of a pressure sensor 26, steam turbine internal actual vapor pressure p3 corresponds to the steam turbine internal desired vapor pressure. In this way, the steam mass flow M is then indirectly controlled by the steam turbine 10, namely via the regulation of the steam turbine internal actual steam pressure p3 to the steam turbine internal desired steam pressure via the control valve 15 of the steam turbine 10th

Preferably, such a steam turbine internal actual vapor pressure p3 is regulated, which corresponds to a pressure of a last stage of the steam turbine 10. Particularly preferred such a steam turbine internal actual vapor pressure p3 is regulated, which corresponds to a pressure of a stage of the steam turbine 10, the exhaust steam 13 is fed to the downstream process 14 as process steam. The steam turbine internal actual vapor pressure p3 to be regulated is detected by measurement using the pressure sensor 26 and supplied to the control device 19.

In Fig. 2 the steam mass flow M is applied through the steam turbine 10 above the actual exhaust steam pressure p2 of the exhaust steam 13 of the steam turbine 10. The characteristic 21 of the Fig. 2 illustrates a steam mass flow-dependent, non-static and therefore dynamic threshold value for the actual steam pressure p2, at which reaching or falling below a protective shutdown of the steam turbine 10 would take place. In the area 23 of the Fig. 2 Accordingly, the steam turbine 10 is switched off protection.

In order to avoid a protective shutdown of the steam turbine 10 as much as possible, the limit value 20 is used according to the invention, the limit of the 21 a has defined distance. If the actual exhaust steam pressure p2 is greater than the steam mass flow-dependent limit value 20, then there is no risk of damage to the steam turbine 10. In the area 22, both the control valve 15 of the steam turbine 10 and the bypass valve 17 of the steam turbine bypass 16 are used to determine the actual exhaust steam pressure p2 to regulate to the desired Abdampfdruck.

If, on the other hand, the actual exhaust steam pressure p2 reaches the steam mass flow-dependent limit value 20 or falls below the limit value 20 up to the characteristic line 21, then the control valve 15 of the steam turbine 10 is no longer used to regulate the actual steam exhaust pressure p2 to the desired exhaust steam pressure; in this case, the control valve 15 of the steam turbine 10 is used to control the steam mass flow M through the steam turbine 10, in which case the steam mass flow M is controlled along the limit value 20 indirectly via the steam turbine internal actual steam pressure p3. The steam mass flow M is proportional to the steam turbine internal actual steam pressure p3 (M~p3) to be regulated.

If, due to a malfunction of the process 13 decreasing the exhaust steam 13, the actual exhaust steam pressure p 2 nevertheless drops below the characteristic curve 21, then the steam turbine 10 is switched off.

With the invention it can be prevented as far as possible that a protective shutdown is performed on a steam turbine 10, without the risk of damaging the steam turbine 10, in particular without the risk of blade damage to the same.

LIST OF REFERENCE NUMBERS

10

steam turbine

11

steam source

12

steam

13

exhaust steam

14

process

15

control valve

16

steam bypass

17

Auxiliary control valve / bypass valve

18

Valve

19

control device

20

limit

21

curve

22

Area

23

Area

24

pressure sensor

25

pressure sensor

26

pressure sensor

Claims (10)

A method of operating a steam turbine (10), wherein the steam turbine (10) is supplied from a steam source (11) steam (12) having a relatively high vapor pressure (p1) for relaxation, and leaving the steam turbine (10) Abdampf (13), which has a relatively low Abdampfdruck (p2), a downstream process (14) is fed as process steam, wherein the actual Abdampfdruck (p2) of the steam turbine (10) leaving the exhaust steam (13) is detected by measurement, and wherein depending on the detected actual exhaust steam pressure (p2), a steam turbine (10) associated control valve (15) and / or an auxiliary control valve (17), in particular a steam turbine bypass (16) associated bypass valve (17) are controlled, characterized in that then, when the actual Abdampfdruck (p2) is less than a limit value or reaches a limit, for controlling the actual Abdampfdrucks (p2) to a target Abdampfdruck exclusively the auxiliary control valve (17) rt, whereas the control valve (15) of the steam turbine (10) is driven to set a steam mass flow (M) through the steam turbine. A method according to claim 1, characterized in that when the actual Abdampfdruck (p2) is less than the limit value or reaches the limit for adjusting the steam mass flow (M) through the steam turbine (10) depending on the detected actual Abdampfdruck (p2 ) an internal steam turbine desired steam pressure is determined and the control valve (15) of the steam turbine (10) is controlled so that a steam turbine internal actual vapor pressure (p3) corresponds to the steam turbine internal desired vapor pressure. A method according to claim 2, characterized in that the steam turbine internal actual vapor pressure (p3) is detected by measurement. A method according to claim 2 or 3, characterized in that depending on the detected actual Abdampfdruck (p2) a maximum allowable steam mass flow through the steam turbine (10) is determined, and that depends on the determined maximum allowable steam mass flow through the steam turbine (10) of steam turbine internal desired steam pressure is determined in order to regulate the steam mass flow (M) through the steam turbine (10) indirectly via the regulation of the steam turbine internal actual steam pressure (p3) to the steam turbine internal desired steam pressure. Method according to one of claims 2 to 4, characterized in that such a steam turbine internal actual vapor pressure (P3) of the steam turbine (10) is controlled, which corresponds to a pressure of a last stage of the steam turbine (10). Method according to one of claims 2 to 5, characterized in that such a steam turbine internal actual vapor pressure (p3) of the steam turbine (10) is controlled, which corresponds to a pressure of a stage of the steam turbine (10) whose exhaust steam (13) the downstream process (14) is supplied as process steam. Method according to one of claims 1 to 6, characterized in that the limit value for the actual exhaust steam pressure (p2), when it reaches or falls below the control valve (15) of the steam turbine (10) is driven to the steam mass flow (M) through the To set steam turbine, a vapor mass flow-dependent limit is. Method according to one of claims 1 to 7, characterized in that when the actual Abdampfdruck (p2) is greater than the limit, for regulating the actual Abdampfdrucks (p2) to the desired Abdampfdruck both the control valve (15) of the Steam turbine (10) and the auxiliary control valve (17), in particular the bypass valve (17) of the steam turbine bypass (16), are controlled. A method according to claim 8, characterized in that the control valve (15) of the steam turbine (10) depending on a difference between the actual Abdampfdruck (p2) and a first target Abdampfdruck and the auxiliary control valve (17), in particular the bypass valve (17). , is driven dependent on a difference between the actual exhaust steam pressure (p2) and a second set exhaust steam pressure. A method according to claim 9, characterized in that the second target Abdampfdruck is smaller than the first target Abdampfdruck.

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