DE102009026053A1 - Overload valve for a steam turbine and associated method - Google Patents

Abstract

A system for operating a steam turbine includes: at least one high pressure turbine section and a low pressure section; one or more control valves configured to introduce steam from a boiler into the high pressure turbine section; a condenser configured to receive steam discharged from the low pressure section and to convert the steam into a liquid; a top heater arranged to receive liquid from the condenser and to heat the liquid via heat exchange with a vapor from the high pressure section and to return the heated liquid to the boiler; and a bypass overload valve configured to supply steam bypassed past the one or more control valves directly to the top heater.

Description

These The invention relates to the operation of a steam turbine using the turbine power reserve for operation under increased Loads.

BACKGROUND TO THE INVENTION

Size Steam turbines of the type used in the electrical power industry are used generously, by a certain additional load power potential over the rated power, an operating point that is usually as the "warranty point" is called to offer. The Nominal power is indicated by the output power, and this Condition becomes conventional with one or more control valves reached, which is not completely open are, so the extra power obtained by fully opening the control valves becomes. If the turbine design is such that the rated power occurs when the steam inlet valves are fully open, The turbine efficiency is at this point in terms of energy use or heat rate significantly improved. However, stand at fully open Control valves have limited funds available, with which a reserve capacity or reserve of a Steam turbine can be achieved.

One known method for obtaining a surplus power in a turbine when the rated power is at full open control valves occurs, is a Provide bypass valve and thereby additional steam around the control valves around at a later, a lower pressure flow stage of the turbine to flow. This Ver drive (as it has been used in the past) points three disadvantages. First, it is considered necessary that Bypass valve to integrate into the turbine control system, thereby the bypass valve in effect to an additional control valve in a controlled and coordinated way throttled with the intake control valves. This increases significantly the complexity of the tax system. Second, it's about increasing regulatory requirements of the industry in a throttling To meet bypass valve, required a certain overlap between to provide the control valves and the bypass valve. In other words It becomes necessary with the opening of the bypass valve begin before the control valves are fully open. This reduces the efficiency of the turbine at its rated output. thirdly is due to the small capacity of such Bypass valve a considerable lifting movement of the valve required to power the turbine to the frequency control in the power system, to which she is connected to participate. This size Movement can cause severe wear and tear lead to premature failure of the valve.

In another method, a bypass overload valve is used to achieve a power reserve of the turbine without significant change to the turbine control system, wherein the bypass steam is reintroduced to a downstream turbine stage. This procedure is in the name of the common denominator U.S. Patent No. 4,403,476 described.

BRIEF DESCRIPTION OF THE INVENTION

In the exemplary but by no means limiting embodiment, as disclosed herein, the one supplied by the kettle and to the overload valve upstream of the steam turbine inlet redirected steam back to the upper heater, instead of being led to a downstream turbine stage to become.

Accordingly, the present invention in one aspect, a system for operating a steam turbine, comprising: at least one high pressure turbine section and a low pressure section; one or more control valves, configured to draw steam from a boiler to the high pressure turbine section permit; a condenser that is set up to be of that Low-pressure section to receive steam output and the steam to convert into a liquid; a top heater, the is set up to liquid from the condenser receive and the liquid through a heat exchange with a steam from the high pressure section to heat and around the returned heated liquid to the boiler; and an overload bypass valve that is set up to pass the one or more control valves redirected steam directly to the top heater.

• (a) Halten des Bypass-Überlastventils im Schließzustand, während die Steuerventile in gesteuerter Weise positioniert werden, um Dampf der Turbine zuzugeben, um eine vorausgewählte Lastleistung zu erhalten;
• (b) wenigstens teilweises Öffnen des Bypass-Überlastventils; und
• (c) Rückführen von Dampf, der durch das Bypass-Überlastventil hindurchtritt, zu dem Obererhitzer.

In yet another aspect, the invention relates to a method of operating a steam turbine that supplies power to a connected load and is configured to receive steam from a steam generation source, the turbine having one or more control valves for controlling the addition of steam to a higher one Having pressurized stages of the turbine and having a bypass overload valve which is connected to receive steam from the steam source, the method comprising the steps of:

• (a) maintaining the bypass overload valve in the closed state while the control valves are positioned in a controlled manner to add steam to the turbine to obtain a preselected load power;
• (b) at least partially opening the bypass overload valve; and
• (c) returning steam passing through the bypass overload valve to the top heater.

BRIEF DESCRIPTION OF THE DRAWINGS

1 shows a simplified schematic representation of a steam turbine power plant in which the turbine uses a bypass overload valve, according to a known device; and

2 shows a simplified schematic representation similar to the 1 However, it is modified to include the subject matter of the exemplary but non-limiting embodiment disclosed herein.

DETAILED DESCRIPTION THE INVENTION

In the power plant after 1 serves a kettle 10 as the source of high pressure steam that supplies the drive fluid to a steam turbine 12 to drive with reheat, which is a high-pressure section (HD section) 14 , a medium-pressure section (MD section) 16 and a low pressure section (ND section) 18 contains. Although the turbine sections 14 . 16 and 18 are illustrated as they are in a series arrangement with each other and with a generator 20 over a wave 22 coupled, other coupling arrangements can be used. It is also to be understood that the invention further disclosed herein is equally applicable and equally applicable to non-reheat turbines having no MD section.

The steam flow path from the boiler 10 runs over a steam line 24 , from the steam to the HD turbine 14 can be removed via one or more inlet control valves (with multiple valves at 25 - 28 are illustrated). Each control valve 25 - 28 is connected to steam to the HD section 14 either via circumferentially arranged nozzle arcs in a sub-application configuration or to a single space in front of the first-stage nozzles in a single-feed configuration. These two configurations are well known in the art. Further, the control valves of a turbine may be operated with the Teilbeaufschlagungseinrichtung either simultaneously, in the full-arc mode, in which case steam to the HD section 14 in a uniform circumferential pattern across the array, such that the turbine operates as a single-acting turbine, or they may be actuated sequentially in the partial arc mode, in which case steam is directed first to one or more nozzle arcs and then to the nozzle Others in turn, when the turbine load increases, is added.

From the HD section 14 discharged steam flows through a reheater 30 in which the temperature of the steam is increased. Subsequently, steam from the reheater to the MD section 16 and then via a connection channel 32 to the ND section 18 directed. From the LP section 18 discharged steam flows to the condenser 34 which changes the state of the fluid from a vapor state, ie steam, to a liquid state, ie water. The water is then returned to the boiler, where it is converted back to steam and returned to the turbine via the one or more control valves.

Although the control of a steam turbine is a very complex and complicated process, the main issues with the turbine operating in a substantially steady-state operating condition are maintaining the speed and load of the turbine. With reference to 1 These variables are controlled by a rule system 38 with feedback controlled / regulated, the control valves 25 - 28 positioned (ie determines its degree of opening) to more or less steam in the turbine 12 involved. Such control systems are well known and the control system 38 can be, for example, of the type as used in the U.S. Patent No. 3,097,488 is described.

Nearly every turbine is designed to provide a reserve capacity to generate power beyond nominal capacity. To gain extra power from the turbine after the control valves have reached their limit position or fully open position is a bypass overload valve 40 between the steam supply line 24 and the reheat point before the reheater 30 connected. For controlling the bypass overload valve 40 is a simple (manual or automatic) on-off control 42 provided the valve 40 to open when the load request is greater than the rated power. For manual operation of the overload valve 40 can use a simple switching device and the valve 40 at the discretion of the operating staff each time the control valves 25 - 28 are completely open, open.

For example, when the control valves 25 - 28 are completely open and the turbine 12 with their rated power working, get extra power by then adding the overload bypass valve 40 is opened. This allows a quantity of steam, the higher pressure sections to bypass the turbine and on the low temperature side of the reheater 30 enter. Alternatively, however, the through the overload valve 40 redirected steam of a lower pressure stage of the high pressure section 14 be added as indicated by the dashed line 44 is displayed. In either case, there is an increase in the total flow of steam into the turbine, which, when maintained, is the turbine 12 allows to generate a larger output power.

By now on 2 Reference is made, in the like reference numerals, which, however, the numeral 1 is prefixed to be used to designate corresponding components, that of the boiler 110 to the overload valve 140 not diverted steam as in the arrangement after 1 rather, it is returned to a downstream turbine stage, but rather via a conduit 46 to a superheater 48 returned to the turbine. Thus, combine the steam, which in the upper heater 48 from the HD section 114 off (or steam taken from another location via a pathway leading through the HP turbine) and the bypass steam entering the top heater via the line 46 enters, with each other, around the liquid condensate from the condenser 134 to heat. The heated condensate runs to the boiler 110 back, where it is converted back to steam and returned to the turbine, while the now cooled steam from the HD section 114 and the line 46 simply drained from the top heater. It will further be understood that the upper load valve (as opposed to the simple on / off operation) may be incrementally opened and / or closed by any suitable known control means, ie, used in a throttled fashion and thus more responsive to cycling conditions.

The exemplary, but in no sense limiting device solves problems with the more conventional facilities are connected. For example, this device eliminates the need after another control stage within the steam turbine, the usually very expensive. Diverting the steam immediately To the top heater also prevents the steam path from being interrupted or is disturbed. The device also eliminates problems in the context of temperature deviations in the turbine structure, the one temperature load or thermal deformation at the site cause the bypass stream enters the vapor path. temperature loads or thermal deformations can lead to larger Clearances between rotating and stationary components lead to increased steam leakage currents and lower efficiency.

While the invention in conjunction with an embodiment has been described currently as the most practical and preferred embodiment, it is to be understood that that the invention is not limited to the disclosed embodiment should be limited, but that on the contrary different Modifications and equivalent arrangements include should be included in the scope and scope of the attached Claims are included.

One System for operating a steam turbine includes: at least a high pressure turbine section and a low pressure section; one or more control valves that are set up to steam from a boiler into the high-pressure turbine section; a condenser configured to discharge from the low pressure section To receive steam and to pour the vapor into a liquid convert; a superheater set up for liquid from the condenser to receive and the liquid over a heat exchange with a vapor from the high pressure section to heat and add the heated liquid to the kettle due; and a bypass overload valve, configured to be connected to the one or more control valves Passed bypassed steam immediately to the upper heater.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 4403476 [0004]
• - US 3097488 [0013]

Claims (9)

A system for operating a steam turbine, comprising: at least one high-pressure turbine section ( 114 ) and a low pressure section ( 118 ); one or more control valves ( 125 - 128 ), which are designed to draw steam from a boiler ( 110 ) to the high pressure turbine section; a capacitor ( 134 ) arranged to move from the low pressure section ( 118 ) to receive discharged steam and convert the steam into a liquid; a top heater ( 48 ) arranged to remove liquid from the condenser ( 134 ) and receive this liquid via a heat exchange with a vapor from the high pressure section ( 114 ) and to heat the heated liquid to the boiler ( 110 ); and a bypass overload valve ( 140 ) arranged to direct the steam diverted around the one or more control valves directly to the superheater ( 48 ). A system for operating according to claim 1, wherein the bypass steam from the overload valve ( 140 ) and steam from the high pressure turbine section (FIG. 114 ) from the upper heater ( 48 ) be derived. System for operating according to claim 1, wherein the bypass overload valve ( 140 ) is movable between an open and a closed position. System for operating according to claim 3, wherein the bypass overload valve ( 140 ) is incrementally movable in a throttling manner. System for operating according to claim 3, wherein the bypass overload valve ( 140 ) is manually movable at the discretion of an operating staff. System for operating according to claim 3, wherein the bypass overload valve ( 140 ) is automatically movable in response to a turbine load indicating signal. Method for operating a steam turbine ( 112 ) which supplies power to a connected load and is arranged to receive steam from a steam generating source, the turbine comprising: one or more control valves ( 125 - 128 ) for controlling the addition of steam to higher pressure stages of the turbine; a capacitor ( 134 ) configured to receive steam discharged from the turbine and to convert the vapor into a liquid; and a bypass overload valve ( 140 ) connected to receive steam from the steam source, the method comprising the steps of: (a) maintaining the bypass overload valve (12); 140 ) in the closed state, while the control valves ( 125 - 128 ) are positioned in a controlled manner to add steam to the turbine to obtain a preselected load power; (b) at least partially opening the bypass overload valve ( 140 ); and (c) returning steam passing through the bypass overload valve to a superheater (FIG. 48 ) configured to receive liquid from the condenser. Method according to claim 7, wherein the bypass overload valve ( 140 ) is manually caused to be opened and closed at the discretion of an operator. Method according to claim 7, wherein the bypass overload valve ( 140 ) is automatically caused to open and close in response to a signal indicative of the turbine load.