power plant system having overload control valve - patent application.pdf

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Patent application title: POWER PLANT SYSTEM HAVING OVERLOAD CONTROL VALVE

Inventors: Martin Bennauer(Bottrop, DE) Edwin Gobrecht (Ratingen, DE) Edwin Gobrecht

(Ratingen, DE) Karsten Peters (Wesel, DE)

IPC8 Class: AF01K1302FI

USPC Class: 60657

Class name: Power plants motive fluid energized by externally applied heat having apparatus

cleaning, sealing, lubricating, purging, standby, or protecting feature

Publication date: 2012-07-12

Patent application number: 20120174584

Abstract:

A power plant system and a method for operating a power plant system are provided. An

overload control valve is disposed in an overload line and can be actuated by means of a

pressure regulator wherein the overload control valve opens before a diverting control valve opens

the valve forming a bypass between the high-pressure steam inlet and the high-pressure steam

outlet as soon as a target valve is exceeded.

Claims:

1-8. (canceled)

9. A power plant system with a steam generator of a steam turbine, comprising: a live steam line

for feeding live steam into the steam turbine; and an overload line which forms a fluidicconnection between the steam generator and an overload stage of the steam turbine, wherein an

overload control valve is arranged in the overload line, and wherein provision is made for a

pressure controller which is designed for actuating the overload control valve .

10. The power plant system as c laimed in claim 9, further comprising a bypass line which

fluidically connects the high-pressure steam inlet to the high-pressure steam exit of the steam

turbine, wherein the bypass line comprises a bypass control valve and the pressure controller is

designed in such a way that a reference value is set, and when the reference value is exceeded

the bypass control valve opens only when the overload control valve is already open.

11. The power plant system as c laimed in claim 9, wherein the steam turbine comprises a high-

pressure turbine section and the overload line is fluidically connected to the feed stage of the

high-pressure turbine section.

12. The power plant system as c laimed in claim 9, wherein the feed stage is designed in such a

way that the steam turbine converts the steam which flows in via the overload line, performing

work.

13. A method for operating a power plant system, comprising: providing the power plant includinga steam turbine and a live steam line for feeding live steam into the steam turbine and into an

overload line; creating a fluidic connection between a steam generator and an overload stage by

means of the overload line; arranging an overload control valve in the overload line; and arranging

a pressure controller on the overload control valve and is designed for actuating the overload

control valve.

14. The method as claimed in claim 13, wherein provision is made for a bypass line which

fluidically connects the high-pressure steam inlet to the high-pressure steam exit , and wherein

provision is made for a bypass control valve, and wherein the pressure controller is designed in

such a way that a reference value is set and when reference value is exceeded the bypass

control valve opens only when the overload control valve is already open.

15. The method as claimed in claim 13, wherein the overload control valve opens at partial load

and at full load.

16. The method as claimed in claim 13, wherein the overload control valve opens at partial load

or at full load.

Value Plastics, Inc.

www.ValuePlastics.com

3,400 configurations of plastic luers and tube fittings in stock

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Top Inventors for class "Power plants"

Rank Inventor's name

1 Eugene V. Gonze

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5 Patrick Benedict Melton
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9/6/13 POWER PLANT SYSTEM HAVING OVERLOAD CONTROL VALVE - Patent application

www.faqs.org/patents/app/20120174584

17. The method as claimed in claim 13, wherein the steam which flows into the steam turbine via

the overload line is expanded, performing work.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is the U.S. National Stage of International Application No.

PCT/EP2010/063846, filed Sep. 21, 2010 and claims the benefit thereof. The International

Application claims the benefits of European Patent Office application No. 09012048.6 EP filed

Sep. 22, 2009. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

[0002] The invention refers to a power plant system with a steam generator and a steam turbineaccording to the preamble of the claims, and also to a method for operating a power plant

system according to the preamble of the claims.

BACKGROUND OF INVENTION

[0003] Power plant systems usually comprise a steam generator and a steam turbine, which are

designed in such a way that the internal energy of steam is converted into mechanical rotational

energy. The generators which are driven by such steam turbines are usually operated at 50 Hz

for the European market or at 60 Hz for the U.S. American market. Modern steam turbines are

exposed to admission of steam which may have a pressure of up to 350 bar and a temperature

of up to 700 C. This steam which is required in the steam turbine is produced in the steam

generator, wherein this represents a challenge for the materials and components of the steam

generator. Especially important components are the load control unit, the pressure control unit

and the rotational speed control unit. In order to be able to operate the required 50 Hz or 60 Hz

constantly over an extended required time period, high demands are made on the control units.

Power plant systems are customarily required for base load operation which leads to the entire

system being constantly s tressed over an extended time period. During a continuous running

operation, the frequency of the steam turbine shaft and also the volume of the steam which is fed

to the steam turbine are essentially constant. It can happen, however, that in the case of asuddenly changing load in the electrical consumer network the torque transmission being applied

to the generator changes, as a result of which the power output of the steam turbine could

change abruptly, which is to be prevented by means of the control unit. A sudden change to the

power output of the steam turbine is also made as a result of a possible malfunction.

[0004] As a rule, a power plant system is operated in constant pressure mode, variable pressure

mode or on-load mode. In the specific case of the load in the consumer network being suddenly

reduced, the steam turbine must transmit a lower level of torque to the generator. This could be

realized by the valves which are arranged for the feed into the steam turbine being closed or by

the steam generator providing a lower volume of steam at a lower pressure.

[0005] In power plant systems of today, t he pressure control units are designed in such a way

that a live steam pressure in a high-pressure steam system is brought to a fixed pressure value

during a start-up of the steam turbine. As a rule, a bypass line is arranged in such a way that the

high-pressure steam inlet of the s team turbine is fluidically connected to the high-pressure

steam exit of the steam turbine.

[0006] Load rejections to station service or to no-load from the nominal power are referred to as

malfunctions. In this case, both the live steam control valve and the reheat control valve closewith a fast rate of travel. Since the steam generator, however, cannot reduce the output so

quickly, the surplus steam has to be directed past t he steam turbine. To this end, a bypass

control valve, which is arranged in the bypass line, opens, as a result of which the surplus steam

is directed past the steam turbine. If the pressure at full load rises above the reference value,

then the overload control valve opens before the bypass control valves open. However, the

surplus steam which is directed around the steam turbine is no longer used to perform work by

expanding, as a result of which the efficiency of the power plant system is altogether reduced.

The bypass control valve is operated in such a way that the pressure reference value of the

bypass line is controlled above a variable pressure line. With a pressure increase over and above

the selected margin, the bypass control valve opens and sets an upper limit on the pressure,

which leads to a loss of power output.

SUMMARY OF INVENTION

[0007] It is at this point that the invention comes in, the object of the invention being to further

develop a power plant system in such a way that a power output loss is further reduced.

[0008] To this end, it is proposed, according to the invention, to provide an overload line which

forms a fluidic connection between the steam generator and an overload stage of the steam

turbine, and to provide an overload control valve which is arranged in the overload line and

actuated via a pressure controller.

[0009] The advantage of the invention is inter alia that from now on, with pressure controlling and

at full load, the surplus s team no longer has to be directed past the steam turbine via a bypass

line, but is fed into the steam turbine via the overload line, albeit to an overload stage.

Downstream of the overload stage, this introduced steam, expanding and performing work, is

converted into rotational energy. This is to be achieved by the overload control valve opening

before the bypass control valve in the bypass line opens if the pressure at full load rises above a

reference value. Therefore, the overload line acts as a type of bypass station, as a result of which

the steam is directed into the steam turbine instead of it being directed past the steam turbine

without being utilized.

[0010] Advantageous developments are disclosed in the dependent claims. In an advantageous

development, the steam turbine is constructed in such a way that the overload stage, which is

fluidically connected to the overload line, is designed in such a way that the inflowing steam is

converted, performing work. Therefore, an optimum use of the thermal energy of the steam is

utilized in order to increase the efficiency of the power plant system as a result.


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[0011] The object which is directed towards the method is achieved according to the c laims. An

essential feature of the method according to the invention is that the pressure controller, which

actuates the overload control valve, is designed in such a way that a reference value can be set

and in the event of this reference value being exceeded the bypass control valve opens only when

the overload control valve is already open.

[0012] The overload control valve advantageously opens at partial load and/or at full load.

[0013] As a result of the power plant system according to the invention, or the method according

to the invention for operating the power plant system, the power plant can be operated in an

altogether more flexible manner since both in load control mode and in initial pressure mode the

overload control valve can be actuated with any power output. A further advantage is that the

starting losses and power output losses are lower since the overload control valve directs the

steam into the s team turbine instead of directing it past the steam turbine into the condenser

without being utilized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention is explained in more detail based on an exemplary embodiment in the

figure. In the drawing:

[0015] FIG. 1 shows a schematic layout of a power plant system,

[0016] FIG. 2 shows a graph.

DETAILED DESCRIPTION OF INVENTION

[0017] The power plant system 1 according to FIG. 1 comprises a steam turbine 2, wherein this

comprises a high-pressure turbine section 2a, an intermediate-pressure turbine section 2b and a

low-pressure turbine section 2c. Via a steam generator 3, live steam finds its way via a live

steam line 4, via a live steam control valve 5, into a high-pressure steam inlet 6 of the high-

pressure turbine section 2a. In addition to the live steam line 4, the power plant sys tem 1

comprises a bypass line 7 which fluidically connects the live steam line 4 to a high-pressuresteam exit 8 of the high-pressure turbine section 2a. A bypass control valve 9 is arranged in the

bypass line 7.

[0018] Furthermore, the power plant system 1 comprises an overload line 10 which fluidically

connects the steam generator 3 to an overload stage 11 of the high-pressure turbine section 2a.

An overload control valve 12 is arranged in the overload line 10.

[0019] As a rule, the overload control valve 12 and the bypass control valve 9 are closed, wherein

the live steam control valve 5 is open and is actuated via a pressure controller or load controller,

which is not shown in more detail.

[0020] The steam which discharges from the high-pressure turbine section 2a is referred to as

cold reheat steam and is heated again in a reheater 13. The steam which discharges from the

reheater 13 is referred to as hot reheat steam 14. This hot reheat steam 14 flows via an

intermediate-pressure control valve 15 into the intermediate-pressure turbine section 2b and is

converted there, expanding and performing work. The steam which discharges from the

intermediate-pressure turbine section 2b is fluidically communicated via intermediate-pressure

discharge lines 16 to t he low-pressure steam inlet 17 of the low-pressure turbine section 2c. The

steam which discharges from the low-pressure turbine sect ion 2c is directed via a low-pressuredischarge line 18 to a condenser 19, converted into water there, and finally, via a feed-water

pump 20, is directed to the steam generator 3, as a result of which a water-steam cyc le is

completed. The steam which is converted from the thermal energy into rotational energy drives a

shaft 21 which in turn drives a generator 22 which ultimately provides electric energy.

[0021] The live steam control valve 5, the overload control valve 12 and the bypass control valve 9

are also arranged in each case on an independent separate pressure controller. The pressure

controller which is responsible for the overload control valve 12 is designed in this case in such a

way that a reference value can be set and in the event of this reference value being exceeded the

overload control valve 12 opens before the bypass control valve 9 opens. The overload control

valve 12 in this case is usually open at full load.

[0022] The steam which flows in via the overload stage 11 is converted, performing work, instead

of being directed past the high-pressure turbine section 2a, via the bypass line 7, without being

utilized. In so doing, the efficiency of the power plant system is further increased as a result.

[0023] For the controlling, a new pressure characteristic line for the overload control valve 12 is

situated between a variable pressure characteristic line of the high-pressure turbine section 2a

and the high-pressure bypass characteristic line. If the live steam pressure rises above this newpressure characteristic line, the overload control valve 12 opens but not the bypass control valve

9. The overload control valve 12 then controls a pressure which is predetermined by the new

pressure characteristic line. As a result, the live steam, via the overload control valve 12, is

utilized in the high-pressure turbine section 2a and not directed past t he steam turbine 2 into the

condenser 19 without being utilized.

[0024] Two operating cases exist in which the live steam which is generated by the steam

generator cannot be fully utilized by the steam turbine. On the one hand, this happens when

running up the power plant from the stationary state to nominal power or nominal rotational

speed, and, on the other hand, if during nominal operation a partial or complete load shedding is

carried out. In this case, the turbine generator set is adjusted to the new demands as quick ly as

possible, wherein the steam generator, however, can follow up only with delays. During this time,

the steam continues to be produced by the boiler until the s team-pressure controller has the

entire steam generation process under control again. The steam volumes which are not absorbed

can be directed either into the atmosphere or the possibility exists of decoupling the steam from

the steam turbine by means of fast-reacting bypass stations and allowing it to flow into the

condenser. Therefore, a closed steam control circuit, from which volumes of steam are no longer

lost, is maintained.


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Patent applications by Edwin Gobrecht, Ratingen DE

Patent applications by Karsten Peters, Wesel DE

Patent applications by Martin Bennauer, Bottrop DE

[0025] FIG. 2 shows pressure curves as a function of the steam mass flow. The live steam

pressure 26 is plotted on the Y-axis and the s team generator mass flow 25 is plotted on the X-

axis. The variable pressure characteristic line 27 represents the customary operating curve. If the

turbine valves are completely open, the steam mass flow volumes at nominal pressure are totally

absorbed by the turbine.

[0026] The reference value characteristic line 28 of the bypass station extends with a pressure

difference P above the variable pressure characteristic 27 line. This has the result that the

bypass s tation is not opened too early. Not until the operating pressure is increased by the

pressure difference are the bypass valves opened.

[0027] According to the invention, an additional characteristic line 29 for the overload valve

control is plotted between the variable pressure characteristic line 27 and the reference value

characteristic line 28. The additional characteristic line 29 lies above the variable pressure

characteristic line 27 and below the reference value characteristic line 28. If the live steampressure 26 during operation rises above that of the variable pressure characteristic line 27, then

the overload control valve 12 opens first and only after that does the bypass control valve 9 open.

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