US20170276432A1

US20170276432A1 - Condenser for a steam power plant

Info

Publication number: US20170276432A1
Application number: US15/503,702
Authority: US
Inventors: Kai Brune; Stefan Brussk; Nigel-Philip Cox; Daniel Dreier; Tobias Gabl-Zimmek; Andrei Ghicov; Marie Hu; Mario Koebe; Marc Lange; Teresa Pott; Stefan Riemann; Andreas Ulma; David Veltmann; Gerta Zimmer
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2014-08-20
Filing date: 2015-08-19
Publication date: 2017-09-28
Also published as: EP2987971A1; DE112015003814A5; WO2016026883A1

Abstract

A method for operating a condenser, wherein the condenser is designed for condensing water vapor to form water and during operation a condensate having water accumulates in the condenser, wherein on the condensate surface a plurality of floating bodies are arranged on the condensate, wherein the floating bodies float on the condensate, wherein a large number of floating bodies are used in such a way that the condensate surface is covered, wherein the floating bodies are of spherical and/or sphere-like design, and wherein floating bodies with different sizes are used.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2015/069010 filed Aug. 19, 2015, and claims the benefit thereof. The International Application claims the benefit of European Application No. EP14181545 filed Aug. 20, 2014. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a method for operating a condenser.

BACKGROUND OF INVENTION

Modern power plants as a rule comprise a gas and steam turbine plant and electric generators which are designed for generating electric energy. The torque-transmitting drive for the electric generators is carried out via the shafts of the gas turbine and/or steam turbine.
During operation, steam, which is produced in a steam generator, flows to a high-pressure turbine section and from there to a reheater in which the steam is brought up to a certain temperature. After the reheating, the steam flows to an intermediate-pressure turbine section and from there flows via a crossover pipe to a low-pressure turbine section. Downstream of the low-pressure turbine section, the steam flows into a condenser and condenses there to form water. In the condenser, the water is collected to form a condensate. The condensate has a condensate surface which in the main is fluidically connected to the flow passage of the steam turbine. Therefore, an evaporating condensate is connected to the fact that via the fluidic connection a certain proportion of water vapor from the condensate flows back into the steam turbine.
The current market requirements lead to the power plant operators having to put their power plants into more frequent, unscheduled shutdown states of unforeseeable duration. This means, however, that after the shutting down of a steam turbine the steam which is present in the steam turbine condenses as soon as the temperature falls below the dew point. As a rule, the seal steam system is no longer in operation after such a shutdown. The combination with the water which is available from the condenser, with the oxygen which is provided by means of the vacuum breaker and the shaft bushing, and with the metal, leads to a possible occurrence of corrosion. Therefore, in the case of a stationary steam turboset the risk of stagnant-condition corrosion inside the turbine casing, valve housings and condensers may exist as soon as the relative air moisture of the ambient air inside the respective components exceeds a limit value or the surface temperature of the metal parts inside the turbine and valve housings and also condensers cools down in such a way that the metal parts can fall below the dew point temperature.
In particular, the final stages of low-pressure turbine sections and the condenser are at risk of corrosion since even during operation their temperatures lie close to the dew point or already lie below it.
In order to be able to put the steam power plant quickly into operation again and in order to minimize the operating costs, the condensate in the hotwell in the condenser is not released and remains inside the condenser. This, however, results in the evaporation leading to an increase of the moisture in the condenser and in the low-pressure turbine section adjoining it.
In order to avoid corrosion, provision is made for installing dry-air equipment after the first day of the shutdown. As a result of the operation using dry-air equipment, dried air from the environment is continuously introduced into the turbine casing and therefore the entry of moist ambient air from the turbine hall is prevented. The introduced dry air absorbs moisture from the inside of the turbine casing and valve housings and also from the condensers and is discharged again at defined openings.

SUMMARY OF INVENTION

The invention has set itself an object of specifying another way of effectively preventing corrosion in the steam turbine after a shutdown.
This object is achieved by means of a method for operating a condenser as claimed.
The evaporation of the condensate is directly dependent on the size of the contact area between water and air. With the invention, the size of the contact area is effectively reduced by floating bodies being arranged on the condensate. The contact area is reduced as a result of the floating bodies. Consequently, the evaporation in the hotwell is also reduced. A lower moisture content is achieved and the risk of local moisture points is especially reduced.
Furthermore, a lower volumetric flow of dry air is required, which leads to a lowering of operating costs during the drying. By means of the invention, the drying of the turbine is therefore effectively supported.
The floating bodies are arranged according to the invention in a sufficiently large number in a floating manner on the condensate surface.
Advantageous developments are disclosed in the dependent claims.
The floating bodies are advantageously of spherical and/or sphere-like design. In this case, shapes such as a strict spherical shape can feature, i.e. the floating body is a sphere with a determined radius. As opposed to this spherical shape, the floating body can also be of sphere-like design, e.g. ellipsoidal.
The floating bodies advantageously have different sizes. Therefore, the condensate surface can be still further effectively reduced since the points between the large floating bodies can be closed off by smaller floating bodies.
Furthermore, in an advantageous embodiment the floating bodies are designed and arranged in such a way that the floating bodies have different shapes. So, in addition to a spherical floating body, sphere-like floating bodies can therefore also be arranged next to each other on the condensate surface. As a result, the condensate surface is likewise effectively reduced.
In a further advantageous development, the floating bodies are designed in such a way that rotation of the floating body is prevented. Due to the impeded rotation of the floating body, it is possible that the same surface always points to the condensate surface and the non-wetted surface points opposite to the condensate surface. As a result, the non-wetted surface remains dry. An increase of the air humidity is prevented as a consequence.
In an advantageous development, the floating bodies have different densities. This leads to the floating bodies being able to be arranged in different layers on the condensate surface. The floating bodies in an advantageous development are provided with a material surface which is as hydrophobic as possible. A hydrophobic surface results in a non-wettable surface. Therefore, the moisture is retained in the condensate.
A further advantage of the invention is that existing condenser plants can be retrofitted without restriction in a very simple and inexpensive manner according to the invention. Since an adaptation to the specific condenser geometry is carried out exclusively via the quantity of floating bodies, the invention can be put into operation inexpensively. No individual installed parts are necessary.
The floating bodies can be secured by measures such as an interconnection or covering against undesirable suction by pumps.
Using the invention, the advantage of attaining a reduced evaporation in the hotwell is therefore achieved. This means that a smaller quantity of moisture is created, as a result of which the air quantity which is required for the drying is reduced in turn. This benefits the drying especially in the region of the low-pressure turbine section and in the region of the final stages. As a result, the cost of drying is lower and regions with increased moisture because of evaporation of the condensate are minimized. Furthermore, the risk of corrosion and the subsequent damage to the turbine which is associated therewith is reduced.
Furthermore, by using a large number of floating bodies no individual adaptation to the shape of the condenser is required. The floating bodies are automatically adapted to the current condenser geometry. Consequently, retrofitting of existing plants is possible in a simple manner.
The characteristics, features and advantages of this invention which are described above, and also the way in which these are achieved, become more clearly and more plainly comprehensible in conjunction with the following description of the exemplary embodiments which are explained in more detail in conjunction with the drawings.
Exemplary embodiments of the invention are described below with reference to the drawings. This drawing is not intended to definitively represent the exemplary embodiments, but rather the drawing, where useful for explanation, is embodied in schematized and/or slightly distorted form. With regard to supplements to the teachings which are directly recognizable in the drawing, reference is made to the applicable prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawing:

FIG. 1 shows a cross-sectional view of a condenser,

FIG. 2 shows a cross-sectional view of a first embodiment according to the invention of the floating bodies,

FIG. 3 shows a further embodiment of the floating bodies according to the invention.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a cross-sectional view of a condenser 1 for a steam power plant, which is not shown in more detail. The condenser 1 comprises a plurality of tube bundles 2 which are arranged in a steam flow 3. Cooled water flows through the tube bundles 2, which leads to the water vapor from the steam flow 3 condensing on the surfaces of the tube bundles 2 and, as water, coming into a region 4 in which the water collects to form a condensate 5. The steam flow 3 is fluidically connected to a low-pressure turbine section. Furthermore, the condenser 1 comprises air coolers 6 which are arranged in the region of the tube bundles 2.
The condensate 5 forms a condensate surface 7.
According to the invention, floating bodies 8 are arranged on this condensate surface 7. In FIG. 1, for reasons of clarity, only three floating bodies 8 are provided with the designation 8. These floating bodies 8 wet the condensate surface 7 and consequently reduce the contact area of the condensate surface 7 with the environment. The floating bodies 8 are of spherical and/or sphere-like design. Optionally, other shapes are also possible, as is the simultaneous use of different shapes and sizes.
Shown in FIG. 2 by way of example is an arrangement in which the floating bodies 8 are arranged one above the other in a plurality of rows, wherein the floating bodies 8 have different sizes and are of spherical design in a first approximation.
FIG. 3 shows a further embodiment of the invention. The floating bodies 8 are of sphere-like design in FIG. 3 and are also arranged one above the other in layers. Similarly, the floating bodies 8 are designed with different sizes.
A further embodiment of the floating bodies 8 lies in the fact that these are of unsymmetrical design, which prevents rotation. As a result, the surface can dry more quickly.
The specific gravity of the floating bodies 8 is different and can be selected so that the steam flow cannot lift these out of the condensate. The floating bodies 8 can also have different weights so that, for example, a better covering of the condensate surface 7 is achieved. By the same token, a different density is suitable for this purpose.
The number of floating bodies 8 is selected to be of sufficient size in order to cover the surface of the condensate in the hotwell 9. The number of floating bodies 8, however, can also be significantly greater in order to therefore form a second layer of floating bodies 8, for example.
The floating bodies 8 are preferably equipped with non-absorbent surfaces so that in the ideal case no wetting of the surfaces takes place.
Although the invention has been fully illustrated and described in detail by means of the preferred exemplary embodiment, the invention is not then limited by the disclosed examples and other variations can be derived by the person skilled in the art without departing from the scope of protection of the patent.

Claims

1.-8. (canceled)

9. A method for operating a condenser, wherein the condenser is designed for condensing water vapor to form water and during operation a condensate consisting of water accumulates in the condenser, the method comprising:

arranging on the condensate surface a plurality of floating bodies on the condensate, wherein the floating bodies float on the condensate,

wherein a large number of floating bodies are used such that the condensate surface is covered,

wherein the floating bodies are of spherical and/or sphere-like design, and

wherein floating bodies with different sizes are used.

10. The method as claimed in claim 9,

wherein floating bodies with different shapes are used.

11. The method as claimed in claim 9,

wherein a large number of floating bodies are arranged in the condenser such that they lie one above the other.

12. The method as claimed in claim 9,

wherein floating bodies with different densities are used.

13. Floating bodies for floating on a condensate in a condenser, comprising:

floating bodies designed for the method as claimed in claim 9.