WO1998015778A1

WO1998015778A1 - Condensate and feedwater course of a steam power plant and steam power plant having the condensate and feedwater course

Info

Publication number: WO1998015778A1
Application number: PCT/EP1997/005489
Authority: WO
Inventors: Wolfgang Henselak; Gerald Twarloh; Dennis Ham
Original assignee: Siemens Aktiengesellschaft
Priority date: 1996-10-08
Filing date: 1997-10-07
Publication date: 1998-04-16

Abstract

A condensate and feedwater course of a steam power plant including a feed pump configuration having a booster pump (5b) and a main pump (5a) downstream of the booster pump, is further constructed in such a way that an especially high design load for the steam power plant is attainable. To that end, a heat exchanger (40) provided as a feedwater preheater (40) is connected between the booster pump (5b) and the main pump (5a) of the feed pump configuration.

Description

CONDENSATE AND FEEDWATER COURSE OF A STEAM POWER PLANT AND STEAM POWER PLANT HAVING THE CONDENSATE AND FEEDWATER COURSE

Background of the Invention: Field of the Invention:

The invention relates to a condensate and feedwater course of a steam power plant having a feed pump configuration including a booster pump and a main pump downstream of the booster pump. The invention also relates to a steam power plant hav- ing such a condensate and feedwater course.

A steam power plant with a steam turbine is typically used to generate electrical energy or to drive a work-producing machine as well. A working medium, typically a water-steam mixture carried in an evaporator loop of the steam power plant, is evaporated in a steam generator. The steam which is produced expands, producing work, in the steam turbine and is then supplied to a condenser. The working medium that is condensed in the condenser is then resupplied to the steam generator through a feedwater path in the form of condensate or feedwater.

Many peripheral conditions must be taken into account in constructing the condensate and feedwater course of that kind of steam power plant. For instance, the working medium leaving the condenser and entering the condensate and feedwater course is only at a slight pressure, yet it must be fed at a high pressure into the steam generator of the steam power plant. In order to assure the requisite elevation of pres- sure for that purpose, a feed pump configuration is typically connected into the condensate and feedwater course. The feed pump configuration may include one or more pumps, depending on the requisite pressure increase. For instance, a first pump may be provided as a booster or auxiliary pump, and a second pump as a main pump. Another parameter that is relevant to the working medium to be supplied to the steam generator of the steam power plant, besides its pressure, is its temperature. In order to assure high overall efficiency of the steam power plant, the working medium is typically preheated before being evaporated. Depending on the construction of the steam power plant, preheating of the working medium can already be carried out before the working medium enters the steam generator. In that case, a heat exchanger intended as a high-pressure pre- heater is typically included in the condensate and feedwater course, downstream of the feed pump configuration.

A heat exchanger provided as a high-pressure preheater is constructed for a pressure of approximately 300 bar. How- ever, in terms of its dimensions, such a heat exchanger is not adaptable to an arbitrarily high design load of the steam power plant, and therefore the condensate and feedwater course limits flexibility in planning the steam power plant.

Summary of the Invention:

It is accordingly an object of the invention to provide a condensate and feedwater course for a steam power plant and a steam power plant having the condensate and feedwater course, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, in which the course can be especially well adapted to a high design load for the steam power plant while not entailing major expense for materials for its components and in which the power plant has a condensate and feedwater course that enables simple ad- aptation to a high design load.

With the foregoing and other objects in view there is provided, in accordance with the invention, a condensate and feedwater course of a steam power plant, comprising a feed pump configuration having a booster pump, a main pump down- stream of the booster pump, and a heat exchanger connected as a feedwater preheater between the booster pump and the main pum .

The invention takes as its point of departure the concept that a condensate and feedwater course which is also suitable for a high design load should also have a suitably dimension- able heat exchanger as a feedwater preheater. Suitable di- mensionability of the heat exchanger can be accomplished by lowering the design pressure from the formerly typical level of about 300 bar. Lowering the design pressure of the heat exchanger to about 150 bar, which is especially suitable for this purpose, can be accomplished by locating the heat exchanger between the booster pump and the main pump.

In accordance with another feature of the invention, the heat exchanger provided as a feedwater preheater can be acted upon on the primary side with bled steam from the steam turbine.

With the objects of the invention in view there is also provided a steam power plant, comprising a water-steam loop; a steam turbine connected in the water-steam loop; and a feed pump configuration connected in the water-steam loop, the feed pump configuration having a booster pump, a main pump downstream of the booster pump, and a heat exchanger connected as a feedwater preheater, the heat exchanger having a secondary side connected in the water-steam loop between the main pump and the booster pump.

The advantages attainable with the invention are in particular that by placing the heat exchanger between the booster pump and the main pump, its design pressure can be chosen to be especially slight. Therefore, only especially slight demands are made of the material forming the heat exchanger and it can be constructed to be lightweight in structure. The engineering work and the effort involved in assembly and installation for the heat exchanger are thus especially minor. Moreover, through the use of a low design pressure, for instance of about 150 bar, the heat exchanger is especially easily adapted in its dimensions to a high design capacity of the steam power plant .

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 condensate and feedwater course of a steam power plant and a steam power plant having the condensate and feedwater course, it is nevertheless not intended to be lim- ited 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 diagrammatic, top-plan view of one exemplary embodiment of a steam turbine system according to the invention;

Fig. 2 is a side-elevational view of the steam turbine system of Fig. 1, as seen along a line II-II of Fig. 1, in the direction of the arrows; and Fig. 3 is a diagrammatic and schematic view of a coal-fired steam power plant with a condensate and feedwater course.

Description of the Preferred Embodiments: Referring now in detail to the figures of the drawings, in which identical parts 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 feed pump configuration 5 is provided on a side of the steam turbine adjacent the condenser 4. A preheater unit 6 is provided on a side of the steam turbine 2 facing the condenser 4. Both a generator 8 located in the vicinity of the steam turbine 2 and the feed pump configuration 5 can be driven by a shaft 7 of the steam turbine 2.

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 flush with 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 coal-fired steam power plant 20 shown in Fig. 3 and communicates with a once- through steam generator 22 of the steam power plant 20. One such once-through steam generator 22 is described, for instance, in co-pending U.S. Patent Application Serial No. (Attorney's Docket No. 5796) entitled "Modular Boiler", filed concurrently with the instant application and having the same assignee. Alternatively, the steam generator 22 may also be designed as a drum-type steam generator. The steam turbine 2, the condenser 4, the preheater unit 6, and the generator 8 are disposed in a common power house or turbine hall 10 shown in Fig. 1.

As is also shown in Fig. 1, the generator 8 is connected through a supply line system 11, into which a switch system 12 is incorporated, to a generator transformer 13, disposed outside the turbine hall 10, that 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 flush with 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. These elements are connected to one another in series. 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. Locating the preheater elements 15 in the common heater rig 14 makes it possible to prefabri^¬ cate the preheater unit 6 as a module. This makes the effort and expense of on-site assembly especially low. As is shown schematically in Fig. 3, the steam turbine 2 of the steam power plant 20 is connected to the once-through steam generator 22 through a water-steam loop 24. The water- steam loop 24 includes a condensate and feedwater course 25, which connects an outlet of the condenser 4 to an inlet of the once-through steam generator 22. The steam turbine 2 is downstream of the condenser 4, which in turn communicates on the outlet side through a condensate pump 26 and a number of the preheater elements 15 of the preheater unit 6, with a feedwater tank 28. The feed pump configuration 5 is connected into the water-steam loop 24 of the steam turbine 2 in order to feed feedwater W from the feedwater tank 28 into the once-through steam generator 22, which is connected on its outlet side to the steam turbine 2.

The feed pump configuration 5, which is drivable by the shaft 7 of the steam turbine 2, includes a main pump 5a and an additional or booster pump 5b upstream of the main pump in the water-steam loop 24. In the exemplary embodiment a hydraulic gear 30 is connected to the shaft 7 of the steam turbine 2 for purposes of force transmission. The main pump 5a in turn communicates with the booster pump 5b through a step-down gear 32. The various shafts having the different rotational speeds are identified by reference numerals 7, 27 and 37.

In the exemplary embodiment, the feed pump configuration 5 is located on the "hot end" of the shaft 7 of the steam turbine 2, that is the end opposite the generator 8. However, it may also be disposed on the "cold end" of the shaft 7 of the steam turbine 2, that is on the same end as the generator 8. Moreover, as is shown in the exemplary embodiment, it is possible for only one feed pump configuration 5 to be drivable by the shaft 7 of the steam turbine 2. As an alternative, though, a plurality of feed pump configurations may be driv- able by the shaft 7 of the steam turbine 2. A heat exchanger 40 which is disposed between the booster pump 5b and the main pump 5a is formed by a number of preheater elements 15. The heat exchanger 40 acts as a feedwater preheater and is connected into the water-steam loop 24 on the secondary side. The heat exchanger 40, which can be acted upon on the primary side by bled steam A from the steam turbine, is constructed for an operating pressure of 150 bar. Due to this construction, which is made possible by the disposition of the heat exchanger 40 between the booster pump 5b and the main pump 5a, the heat exchanger 40 can be constructed with a lightweight type of construction. Due to the low design pressure of about 150 bar of the heat exchanger 40, the engineering efforts and especially the effort and expense for assembly and installation are especially slight .

Claims

We claim :

1. A condensate and feedwater course of a steam power plant, comprising :

a feed pump configuration having a booster pump, a main pump downstream of said booster pump, and a heat exchanger connected as a feedwater preheater between said booster pump and said main pump.

2. The condensate and feedwater course according to claim 1, wherein said heat exchanger connected as a feedwater preheater has a primary side to be acted upon with bled steam from a steam turbine of the steam power plant .

3. A steam power plant, comprising:

a water-steam loop;

a steam turbine connected in said water-steam loop; and

a feed pump configuration connected in said water-steam loop, said feed pump configuration having a booster pump, a main pump downstream of said booster pump, and a heat exchanger connected as a feedwater preheater, said heat exchanger having a secondary side connected in said water-steam loop between said main pump and said booster pump.