WO1998016724A1

WO1998016724A1 - Steam turbine and steam power plant with the steam turbine

Info

Publication number: WO1998016724A1
Application number: PCT/EP1997/005490
Authority: WO
Inventors: Armin Drosdziok; Andreas FELDMÜLLER; Dennis Ham
Original assignee: Siemens Aktiengesellschaft
Priority date: 1996-10-15
Filing date: 1997-10-07
Publication date: 1998-04-23
Also published as: TW373052B

Abstract

A steam turbine includes a first pressure stage having a steam outlet side communicating through an overflow line with a second pressure stage. The steam turbine should be suitable for supply with an especially great number and kind of fresh-steam states and to that end, a water separator is incorporated in the overflow line.

Description

STEAM TURBINE AND STEAM POWER PLANT WITH THE STEAM TURBINE

Background of the Invention: Field of the Invention: The invention relates to a steam turbine having a first pressure stage with a steam outlet side communicating with a second pressure stage through an overflow line. It also relates to a steam power plant having such a steam turbine.

A steam power plant is typically used to generate electrical energy or to drive a work-producing machine. To that end, an operating medium carried in a water-steam loop of the steam power plant, and in particular a water-steam mixture, is evaporated in an evaporator. The resultant steam is supplied to a steam turbine, where it expands, performing work. The expanded steam is carried to a condenser, where it condenses. The resultant condensate is resupplied to the evaporator, through a condensate and feedwater path.

In order to attain high efficiency in such a steam power plant, the steam turbine is typically constructed in multiple stages, in particular with three stages. The typically superheated fresh steam generated in a steam generator encompassing the evaporator is first supplied to the high- pressure portion of the steam turbine, where it partially expands. The steam, thus relieved from a high pressure to a medium pressure, is then supplied to the medium-pressure portion of the steam turbine, where it expands further. The steam, thus further relieved to a low pressure level is then carried to the low-pressure portion of the steam turbine. There, it expands completely.

In order to provide especially good adaptation to given steam conditions, and in particular with respect to the steam temperature and steam pressure, the pressure stages of the steam turbine are constructed differently. The high-pressure and medium-pressure portion of the steam turbine may be combined in one pressure stage and disposed in a common housing. The medium-pressure portion, or the combined high- pressure and medium-pressure portion of the steam turbine typically communicates on the steam outlet side with the low- pressure portion of the steam turbine through an overflow line.

In a fossil-fueled steam power plant, an intermediate superheater of the partially expanded steam may be provided between the pressure stages of the steam turbine. The partially expanded steam is first resupplied to the steam generator where it is superheated, before being fed into the next pressure stage. An overly high moisture content in the steam which could cause a loss of efficiency or even corrosion in the steam turbine is avoided by supplying superheated steam to the medium-pressure portion or the low-pressure portion of the steam turbine. However, such intermediate superheating is expensive, especially in terms of planning and installation of the pipelines and superheater heating surfaces required for it. Moreover, that kind of steam power plant is only limitedly flexible with respect to the fresh steam states which can be fed into the steam turbine.

Summary of the Invention: It is accordingly an object of the invention to provide a steam turbine and a steam power plant with the steam turbine, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which are suitable for an especially wide range of operating states of fresh steam to be supplied to the steam turbine.

With the foregoing and other objects in view there is provided, in accordance with the invention, a steam turbine, comprising a first pressure stage having a steam outlet side; an overflow line; a water separator incorporated in the overflow line; and a second pressure stage communicating through the overflow line with the steam outlet side of the first pressure stage.

The invention is based in particular on the concept that the steam turbine, for the sake of especially great flexibility with regard to the fresh steam state, should also be constructed for a high moisture content in the steam. This is attainable even without intermediate superheating of the steam, and thus by especially simple provisions, by extracting moisture from the steam flowing out of the first pressure stage. The water separator, which is incorporated in the overflow line connecting the first pressure stage to the second pressure stage, is especially suitable for that purpose.

In accordance with another feature of the invention, there is provided an intermediate superheater incorporated into the overflow line. This is done in order to increase efficiency and to achieve especially flexible adaptation of various fresh steam states to the prevailing operating state of the steam turbine.

In accordance with a further feature of the invention, the intermediate superheater is heated through the use of steam, especially bled steam from the steam turbine.

In accordance with an added feature of the invention, in order to provide especially effective water separation, the water separator has a number of deflector elements. Water separation is based on separating water from steam in the wet steam as a consequence of the differing centrifugal acceleration upon the deflection of the wet steam. The specifically heavier and thus more sluggish water is pressed against the deflector elements, while conversely the specifically lighter and thus less-sluggish steam adapts its flow direction preferentially to the deflector elements.

In accordance with an additional feature of the invention, there is provided a guide baffle as each deflector element having a flow surface communicating with a water outlet. The water from the wet steam precipitates out onto the flow surface and is then delivered to the water outlet.

In accordance with a concomitant feature of the invention, the steam turbine is part of a fossil-fueled and in particular coal-fired steam power plant. It is precisely in combination with a fossil-fueled or expediently coal-fired steam power plant that an especially great widening of the parameter range for the fresh steam to be supplied to the steam turbine is attainable with this kind of steam turbine.

The advantages attained with the invention are in particular that because of the disposition of the water separator in the overflow line connecting the first pressure stage to the second pressure stage, an excessive moisture content in the steam supplied to the second pressure stage is reliably avoided. The steam turbine can thus be supplied with a particularly great number and kind of fresh steam states. In particular, utilizing the differing specific density of water and steam through the use of deflection of the flow direction enables reliable separation of the wet steam by especially simple provisions.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a steam turbine and a steam power plant with the steam turbine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings .

Brief Description of the Drawings:

Fig. 1 is a top-plan view of a steam turbine system;

Fig. 2 is a side-elevational view of the steam turbine system which is taken along a line II-II of Fig. 1, in the direction of the arrows; Fig. 3 is a schematic circuit diagram showing a condensate and feedwater path in a coal-fired steam power plant; and

Fig. 4 is a fragmentary, diagrammatic view of an overflow line located in a portion IV of Fig. 3.

Description of the Preferred Embodiments:

Referring now in detail to the figures of the drawings, in which the same elements are identified by the same reference numerals, and first, particularly, to Fig. 1 thereof, there is seen a steam turbine system 1 which includes a steam turbine 2 with a high-pressure and medium-pressure portion 2a and a low- pressure portion 2b, to which a condenser 4 is connected radially on the downstream side. A preheater unit 6 is disposed on a side of the steam turbine 2 facing the condenser 4. A generator 8 located in the vicinity of the steam turbine 2 can be driven through a steam turbine shaft 7.

Both the high-pressure and medium-pressure portion 2a and the low-pressure portion 2b of the steam turbine 2 as well as the condenser 4 and the preheater unit 6 and the generator 8 are each constructed as a module and are moreover disposed close to the ground. The term "module" should be understood in this case to mean a connectable, transportable component that can be pre-assembled. Each of the aforementioned modules is mounted on a sledlike structure or skid in a non-illustrated manner and can thus be shifted about especially easily. The steam turbine system 1 is part of a non-illustrated coal- fired steam power plant having a high-pressure preheater in the form of a module 9, which is likewise disposed close to the ground on the side of the steam turbine 2 facing the condenser 4. The steam turbine system 1 communicates with a once-through steam generator of the steam power plant. One such once-through steam generator is described, for instance, in co-pending U.S. Patent Application Serial No. (Attorney's Docket No. 5796) entitled "Modular Boiler", filed on or about the filing date of the instant application and having the same assignee. The steam turbine 2, the condenser 4, the preheater unit 6, the generator 8 and the module 9 are disposed in a common power house or turbine hall 10.

The generator 8 is connected through a supply line system 11, into which a switch system 12 is incorporated, to a generator transformer 13 that is disposed outside the turbine hall 10 and serves to transform electrical voltage furnished by the generator 8 to a higher level.

Fig. 2 is a side view of the turbine hall 10, showing the disposition of the steam turbine 2, the condenser 4 and the preheater unit 6 close to the floor. The condenser 4 is radially connected to the steam turbine 2 on the downstream side. The condenser 4, that is constructed as a module, includes a first condenser element 4a and a second condenser element 4b located above the first. An especially space- saving, compact construction is thus achieved.

The preheater unit 6, that is also constructed as a module, includes a number of preheater elements 15 disposed in a common support stand or heater rig 14. Each preheater element 15 can be acted upon with bled steam A from the steam turbine 2 through a bled steam duct system 16. The pressure and temperature of the bled steam A are functions of the location, wherever it is, at which the steam turbine 2 is bled. Each preheater element 15 is constructed for a specific pressure range of the bled steam A. Placing the preheater elements 15 in the common heater rig 14 makes it possible to prefabricate the preheater unit 6 as a module. This makes the effort and expense of on-site assembly especially low. In order to even further facilitate assembly of the steam turbine system 1, the module 9 is also mounted on a sled structure or skid.

As is shown in Fig. 3, the high-pressure and medium-pressure portion 2a of the steam turbine 2 acts as a first pressure stage having a steam outlet side which communicates through an overflow line 30 with the low-pressure portion 2b that acts as a second pressure stage of the steam turbine 2. The high- pressure and medium-pressure portion 2a, which is disposed in a non-illustrated common housing, includes a high-pressure portion 32 and a medium-pressure portion 34 of the steam turbine 2. A water separator 36 and an intermediate superheater 38 are disposed in succession in the overflow line 30. The intermediate superheater 38, which contributes to an especially high efficiency of the steam turbine 2, can be heated through the use of the bled steam A from the steam turbine 2.

As is shown in Fig. 4, which is an enlarged view of the portion IV of Fig. 3, the water separator 36 that is integrated with the overflow line 30 has a number of deflector elements 40. A guide baffle 42 which is provided as each deflector element 40, is pierced by an opening 44. The opening 44 communicates through a water collector 46 with a pipe system leading into the outer region of the overflow line 36, in a non-illustrated manner. This pipe system serves to carry away the separated water. The deflector elements 40 are disposed in a three-dimensional or spatial region of the overflow line 30 in which a change in direction of steam D flowing through the overflow line 30 occurs anyway. This change in direction is reinforced through the use of the deflector elements 40, where a separation of the wet steam D into water and steam also takes place. The water, which is specifically heavier than the steam, is pressed to an increased extent against the flow surfaces of the baffles 42 by centrifugal force. There, it precipitates out. The thus- precipitated water is removed through the water outlet 44 of each deflector element 40 and can thus be carried away. Thus by utilizing centrifugal force, reliable demoistening of the steam D flowing through the overflow line 30 is accomplished by especially simple provisions.

Instead of the water separator 36 shown in Fig. 4, an arbitrary device that acts physically to demoisten the steam D can also be used.

The overflow line 30 may be disposed arbitrarily, in three- dimensional terms. In particular, a disposition of the overflow line 30 vertically above the shaft 7 of the steam turbine 2, or horizontally next to the shaft 7 of the steam turbine 2, is possible.

Claims

We claim :

1. A steam turbine, comprising:

a first pressure stage having a steam outlet side;

an overflow line;

a water separator incorporated in said overflow line; and

a second pressure stage communicating through said overflow line with said steam outlet side of said first pressure stage.

2. The steam turbine according to claim 1, including an intermediate superheater incorporated in said overflow line.

3. The steam turbine according to claim 2, wherein said intermediate superheater is steam-heated.

4. The steam turbine according to claim 1, wherein said water separator has a number of deflector elements.

5. The steam turbine according to claim 4, wherein each of said deflector elements is a guide baffle having an opening formed therein and having a water collector.

6. A fossil-fueled steam power plant, comprising: a steam turbine having:

a first pressure stage having a steam outlet side;

an overflow line;

a water separator incorporated in said overflow line; and

7. A coal-fired steam power plant, comprising:

a steam turbine having:

a first pressure stage having a steam outlet side;

an overflow line;

a water separator incorporated in said overflow line; and