EP1576331B1 - Power plant condenser with deaeration/degassing system - Google Patents

Description

Technical area

The invention relates to the field of power plant technology. It relates to a power plant condenser with a venting / degassing system according to the preamble of claim 1.

State of the art

Power plant capacitors are devices that result in the reduction of the backpressure of steam boilers by reducing the exhaust steam. They have the task to dissipate the not converted into electricity heat of the steam to the environment.

For example, surface capacitors which consist of a boiler with a built-in tube system are known. Turbine steam flows during operation of the power plant via an inlet, the condenser neck, in the condensation chamber, where it is on the outside the condenser tubes, which are traversed by a coolant, usually cooling water, is deposited. The resulting condensate is collected in a condensate collection vessel, the Hotwell, in the lower part of the condenser and fed back into the water-steam circuit by means of condensate pumps. It passes through the preheater and the feedwater pipe into the boiler, where it is vaporized again and drives the turbines as working steam.

The capacity of the condenser significantly influences the efficiency of the entire system and thus the generator output via the turbine counterpressure.

As the condenser pressure is below the atmospheric pressure, some leakage air continuously penetrates into the condenser. This air and other non-condensable components, such. B. endogenous non-condensable Radiolysegase (= non-condensable mixture of H ₂ and O ₂ from the stoichiometric decomposition of water) must be removed from the capacitors.

For this purpose, deaerators or deaerators are used, which are connected to the capacitors so that they aspirate a gas / vapor mixture at a point of the lowest possible vapor pressure and the highest possible gas concentration from the condensation space of the capacitors.

The reason for this measure lies in the deterioration of the condensation performance and thus the condensation pressure in power plants caused by the reduction of the heat transfer coefficient due to the presence of even low concentrations of non-condensable components, which are also referred to as inert gases.

This deterioration is already detectable at a fraction of percent in molar fraction and causes from about 1% (mole fraction air = 0.01) a massive deterioration of heat transfer. In order to minimize this effect, so-called air coolers are installed in the condensation chamber.

Air coolers are funnel-shaped sheet metal structures in the pipe network. They cause a spatial acceleration of the steam / inert gas mixture, so that the steam velocity at the pipe web by the self-sucking effect of the condensation and the suction system does not fall too low and remains in the range of 2-3 m / s. This partially reduces the negative effect of the non-condensable gases. At the end of the funnel-shaped air cooler, the gas / vapor mixture, which has an inert gas content of a few percent to about 20% in molar fraction (mole fraction air = 0.2), through the Saugeraggregate, z. B. vacuum pumps, removed to the outside. Furthermore, the enrichment of the inert gases in the mixture results in a significant reduction in the mass / volume flow of the mixture to be aspirated.

• Verbesserung der Leistung der Vakuumpumpen (tiefer Saugdruck)
• Verringerung der erforderlichen Vakuumpumpleistung
• Verringerung des Verlustes an Kreislaufstoff (reines Wasser)

The air cooler arranged inside the condenser thus has the function of achieving the highest possible enrichment of the inert gases (non-condensable gases) in the mixture, since the following advantages are to be achieved thereby:

• Improvement of the performance of the vacuum pumps (low suction pressure)
• Reduction of the required vacuum pumping capacity
• Reduction of the loss of circulatory substance (pure water)

If the concentration of the non-condensable components is too small, the entraining effect of the steam excess additionally thermally stresses the sucker, causing cavitation problems in the case of the use of water ring pumps and water aspirators, whereas steam aspirators are less sensitive to this phenomenon.

The loss of condensation power due to the presence of inert gases is massive. Thus, the condensation capacity is typically 20-30 kW / m ² in the Hauptkondensatorberohrung, it can sink in the pre-cooler and air cooler space to 0.3-0.5 kW / m ² . This corresponds to a reduction of the heat flux densities by one and a half orders of magnitude.

A disadvantage of this known state of the art is that in power plants often insufficient suction capacity occurs, especially in the capacitor retrofitting of boiling water reactors with simultaneous increase in power. Then the existing suction capacity is usually no longer sufficient for the newly set pressure and the current thermal performance.

But even in conventional and nuclear plants with pressurized water reactors problems are known by insufficient suction capacity. The cause is z. As in non-adequate bundle designs, perforations and leaks in the pipes and in improving the vacuum by retrofitting, for which the existing suckers are not designed.

Another disadvantage of the known prior art, for example, in the pressure loss via the suction line.

DE 199 24 853 A1 discloses a capacitor module system with a device for warming up and degassing make-up water, which is arranged between the module walls of the capacitor modules and in which the make-up water flows in direct contact in countercurrent to the turbine exhaust steam.

Presentation of the invention

The aim of the invention is to avoid the mentioned disadvantages of the prior art. The invention is based on the object to develop a power plant condenser with a venting / degassing, with which it is possible with converted capacitors even with new pressure and increased thermal performance sufficient suction power with the original Saugeraggregat, d. H. So without replacement / conversion of the original Saugeraggregates to achieve. In addition, the pressure loss is to be reduced via the suction line and cavitation problems are avoided especially in Saugeraggregaten with water ring pumps and water jet pumps.

According to the invention this object is in a power plant condenser, which has a condensate collection and optionally an air cooler, and a venting / degassing with an externally arranged Saugeraggregat and a suction line for a vapor / inert gas mixture, wherein said suction line the condenser or in the presence of an air cooler the Lüftkühler of the condenser with the Saugeraggregat connects, solved in that in said suction line, a device for direct contact condensation is arranged, which can be flowed through by direct contact of the vapor / inert gas in countercurrent to erkaltetem condensate from the condensate collector.

The advantages of the invention are that it is possible with the inventive system to achieve an enrichment of the concentration of the non-condensable components while reducing the mass / volume flow of the suction mixture. As a result, in the case of converted capacitors, even with new pressure and increased thermal performance, a sufficient suction power can be achieved with the original vacuum unit, ie without replacement / retrofitting of the original vacuum unit. In addition, the pressure loss via the suction line is reduced, because the volume flow reduced. Cavitation problems especially with suction units with water ring pumps and water jet pumps are avoided because the gas mixture is removed from the cavitation boundary. Further advantages are that the resistances of the wall and fouling, which worsen the heat transfer coefficient, are eliminated by the direct contact condensation. Due to the constant destruction / new formation of the material and temperature boundary layers in the device for direct contact condensation (start-up conditions) can be achieved in both phases by the flow deflection good transport performance.

It is advantageous if the device for direct contact condensation consists of at least one packed column. Further advantageous alternatives are step / ground contact devices or spray devices.

It is expedient if the device for direct contact condensation is installed outside the capacitor. If sufficient space is available, the device may also be arranged inside the capacitor.

Furthermore, it is advantageous if the condensate collecting vessel branches off a first condensate line with a condensate pump arranged therein, downstream of the condensate pump from the first condensate line branches off a second condensate line which is connected to a flowed through by cooling water tube or plate heat exchanger, in which the condensate to a temperature is cooled near the cooling water inlet temperature, and if from the tube or plate heat exchanger, a third condensate line for the cooled condensate to the device for direct contact condensation. In this device, liquid distribution devices, such as a spray device, are arranged. If the condensate is guided in such a way, that is branched off after the condensate pump and passed to the condenser using the recirculation line, it is advantageously ensured that even when starting or in partial load operation Minimum quantity is available. In addition, the required amount of condensate is very small. The cooling of the condensate from the condensation temperature to about the cooling water inlet temperature can be particularly well realized in tube or Plattenwärmeübertragem.

Furthermore, it is advantageous if the device for direct contact condensation has a siphon for the condensate mixture from the recirculated cold condensate and condensate newly formed in the device and the siphon opens into the condenser such that a venting of the condensate mixture takes place as a wet wall column.

Finally, it is advantageous that the composition of the mixture can be controlled by changing the cold condensate stream and / or its temperature.

Brief description of the drawings

Fig. 1

eine schematische Darstellung des Schaltschemas des erfindungsgemässen Kraftwerkskondensators mit Entlüftungs-/Entgasungssystem und

Fig. 2

ein vergrössertes Detail aus Fig. 1, welches die Vorrichtung zur Direktkontaktkondensation zeigt.

In the drawing, an embodiment of the invention is shown. Show it:

Fig. 1

a schematic representation of the circuit diagram of the inventive power plant condenser with venting / degassing and

Fig. 2

an enlarged detail of Fig. 1, which shows the device for direct contact condensation.

In the figures, the same positions are respectively provided with the same reference numerals. The direction of flow of the media is indicated by arrows.

Ways to carry out the invention

• Fig. 1 zeigt eine schematische Darstellung des Schaltschemas des erfindungsgemässen Kraftwerkskondensators mit Entlüftungs-/Entgasungssystem, während Fig. 2 ein vergrössertes Detail aus Fig. 1 zeigt.

The invention with reference to an embodiment and the Fig. 1 and 2 will be explained in more detail.

• Fig. 1 shows a schematic representation of the circuit diagram of the inventive power plant condenser with venting / degassing, while Fig. 2 shows an enlarged detail of Fig. 1.

For a better understanding of the invention, it is expedient to consider both figures together.

The condenser 1 has a condenser neck 2, a vapor dome 3, condenser tubes 5 arranged in the condenser space 4 and an air cooler 6 and an inlet water chamber 7, an outlet water chamber 8 and a condensate collecting tank 9 (hot well). From the condensate collecting 9 branches off a first condensate line 10, in which a condensate pump 11 is arranged.

Downstream of the condensate pump 11 branches off from the line 10 from a second condensate line 12, which leads to the entry of a plate heat exchanger 13. In line 12, a throttle device for regulating the condensate mass flow and reducing the pressure of about 40-50 bar is arranged at 2-3 bar, which is very important for the plate heat exchanger 13.

The outlet of the plate heat exchanger 13 is connected to a third condensate line 14, which leads to a device consisting of at least one packing column 17 for direct condensation 15 and opens into the part of the device 15, which is located above the packing column 17. In line 14, an aperture 27 is arranged, which serves to cause no two-phase flow in the water supply line. At the end of the condensate line 14 is a Liquid distribution device 23 for the cold condensate 24 is arranged. The device 15 is arranged outside of the capacitor 1 in this embodiment.

The known packing column 17 consists of internals with a very large surface area. From the lower part of the device 15, which is located below the packing column 17, a siphon 18 branches off. The siphon 18 opens into the condenser 1 such that a venting of the condensate mixture takes place as a wet wall column.

In the lower part of the device 15, a suction line 19 for the vapor / inert gas mixture 20 coming from the air cooler 6 opens.

From the upper part of the device 15, a suction line 21 for the reduced in the packing column 17 volume flow of the steam / inert gas mixture 20 branches off. The suction line 21 opens into the suction unit 22. The suction unit 22 is a vacuum pump, for example a water jet pump, a water ring pump or a steam jet vacuum.

The system works as follows:

Turbine steam 25 flows through the condenser neck 2 and the steam dome 3 of the condenser 1 in the condensation space 4. Cooling water 26 is uniformly supplied via the inlet water chamber 7 to the condenser tubes 5, flows through the condenser tubes 5 and leaves via the outlet water chamber 8, the condenser 1. Auf the outer side of the condenser tubes 5 condenses the turbine exhaust steam 25 and outputs the heat of condensation to the cooling water 26 in the interior of the tubes 5 from. The resulting condensate is collected in the condensate collection 9 and fed via the line 10 by means of condensate pump 11 to the water vapor cycle again.

A portion of the condensate is diverted after the condensate pump 11 from the line 10 and recirculated to the condenser 1, so that when starting or at partial load, a minimum amount is present. The amount of condensate required for this purpose is low. For example, it is about 3-5 kg for a ratio of 1 to 30-40 for sloshable mass flow to cold condensate for a class 300 MWe condenser.

The condensate attributable to the condenser 1 is supplied via the line 12 to the plate heat exchanger 13. Since this is fed with cold cooling water 25, there takes place a heat exchange. There is a cooling of the condensate from the condensation temperature to about 1 K Gravency with respect to the cooling water inlet temperature. Instead of a plate heat exchanger, a tube heat exchanger can also be used well. In these apparatuses, however, one should provide a 100% redundancy, as an alternative to be cleaned.

The cold condensate 24, which now has a temperature close to the inlet temperature of the cooling water 26, is subsequently supplied via the line 14 to the device 15 consisting of at least one packing column 17 and distributed to the packing column 17 via a liquid distribution device 23, for example spray nozzles. The at least one packing column 17 is known to consist of random packings or structured packings with a very large surface area. For example, the volume-specific transfer area of the pack of a product available on the market is about 250 m ² / m ³ . A bore with an outer diameter of 24 mm and a web of 8 mm gives about 85 m ² / m ³ .

The at least one packing column 17 is flowed through in direct contact in counterflow of cooled condensate 24 and the vapor / inert gas mixture 20, which is introduced from the air cooler 6 via the suction line 19 in the lower part of the device 15. Due to the direct contact and the large surface of the packing, which leads to high residence times and Turbulence lead, the heat transfer is significantly improved. The condensation of a portion of the vapor in the vapor / inert gas mixture 20 therefore occurs. The reduction of the vapor fraction reduces the total mass flow of the vapor / inert gas mixture 20, which is supplied to the suction unit 22 via the suction line 21.

In one example, it has been determined that the volumetric flow can be reduced by 35-45%, reducing the pressure loss in the suction line 21 by more than half. The pressure drop across the packing is less than 1 mbar at a load factor of 1.72 at the sump end of the packing. By increasing the ratio of liquid volume flow (cold condensate 24) to counterflow (steam / inert gas mixture 24), the volume reduction can be improved even more.

By changing the cold water flow and / or its temperature, the composition of the mixture can be controlled cleanly.

Of course, the invention is not limited to the embodiment described. For example, the device 15 may also be arranged inside the condenser 1, if sufficient space is available, or it is possible entirely to dispense with the internal air cooler 6 in the condenser 1 due to the device 15. Except packing columns 17 are as devices 15 also advantageous tray columns, stepped columns or simply spray devices used. In addition, instead of the plate heat exchanger and a tube heat exchanger can be arranged in the system.

• Verbesserung der Saugkapazität, speziell bei umgerüsteten Kondensatoren, wenn die bestehenden Saugeraggregate für den neu eingestellten Druck und die aktuelle thermische Leistung nicht mehr ausreichend sind. Die Anwendung dieses Konzeptes stellt eine technisch und wirtschaftlich günstigere Alternative zum Ersatz/zur Umrüstung des Saugeraggregates dar.
• Verschiebung des "cut-off"-Kondensatordruckes zu tieferen Teillastwerten
• Reduzierung des Kreislaufwasserverlustes durch Absaugung
• Ergänzung und/oder teilweiser bzw. vollständiger Ersatz des internen Luftkühlers des Kondensators
• Verringerung des Druckverlustes über die Saugleitung durch Reduktion des Volumenstromes des Gasgemisches
• Gewinnung von Abstand von der Kavitationsgrenze von Wasserringpumpen und Wasserstrahisaugem

The following advantages arise when using the invention:

• Improvement of the suction capacity, especially with converted capacitors, if the existing vacuum units are no longer sufficient for the newly set pressure and the current thermal power. The application of this concept represents a technical and economically cheaper alternative to replace / retrofit the Saugeraggregates.
• Shift of cut-off condenser pressure to lower partial load values
• Reduction of circulation water loss through suction
• Supplement and / or partial or complete replacement of the internal air cooler of the condenser
• Reduction of the pressure loss via the suction line by reducing the volume flow of the gas mixture
• Obtaining distance from the cavitation limit of water ring pumps and water aspirators

LIST OF REFERENCE NUMBERS

1

capacitor

2

condenser neck

3

steam dome

4

condensation chamber

5

condenser tubes

6

air cooler

7

Admission water chamber

8th

Outlet water chamber

9

condensate tank

10

First condensate line

11

condensate pump

12

Second condensate line

13

Tubular or plate heat exchanger

14

Third condensate line

15

Device for direct contact condensation

16

throttling device

17

packing column

18

siphon

19

suction

20

Steam / inert gas mixture

21

suction

22

suction unit

23

liquid distribution

24

Cold condensate

25

turbine exhaust steam

26

cooling water

27

cover

Claims (11)

1. Power plant condenser (1) with a deaeration/degasification system, wherein the power plant condenser (1) has a condensate collecting vessel (9) and optionally an air cooler (6), and wherein the deaeration/degasification system comprises in essence an external suction unit (22) and a suction pipe (19,21) for a steam/inert gas mixture (20) and the said suction pipe (19,21) connects the condenser (1), or in the presence of an air cooler (6), connects the air cooler (6) of the condenser (1) to the suction unit (22), characterized in that a device (15) for direct contact condensation is installed in the suction pipe (19,21) which device is connected to the condensate collecting vessel (9) by condensate pipes (10,12,14) and which device during the operation, is flow-washed by the steam/inert gas mixture (20) in direct contact in counterflow with the cooled condensate (24) from the condensate collecting vessel (9).
2. Power plant condenser (1) according to Claim 1, characterized in that a first condensate pipe (10) with a condensate pump (11) installed therein branches, a second condensate pipe (12) branches from the condensate collecting vessel (9), from the first condensate pipe (10) downstream of the condensate pump (11) which second condensate pipe is connected to a shell-and-tube- or plate heat exchanger (13) flow-washed by cooling water, in which the condensate is cooled to a temperature close to the cooling water inlet temperature, and in that a third condensate pipe (14) for the cooled condensate (24) from the shell-and-tube- or plate heat exchanger (13) leads to the device (15) for direct contact condensation.
3. Power plant condenser (1) according to Claim 1, characterized in that the device (15) comprises at least one packed column (17).
4. Power plant condenser (1) according to Claim 1, characterized in that the device (15) comprises a staged/plate contact apparatus.
5. Power plant condenser (1) according to Claim 1, characterized in that the device (15) comprises a spray device.
6. Power plant condenser (1) according to Claim 1, characterized in that the device (15) is installed outside the condenser (1).
7. Power plant condenser (1) according to Claim 1, characterized in that the device (15) is installed inside the condenser (1).
8. Power plant condenser (1) according to Claim 3, characterized in that above the packed column (17) a fluid distribution device (23) is installed.
9. Power plant condenser (1) according to one of Claims 1 to 8, characterized in that the device (15) for direct contact condensation has a syphon (18) for the condensate mixture from the returned cold condensate (24) and the condensate newly formed in the device (15) and the syphon (18) runs into the condenser (1) in such a way that a deaeration of the condensate mixture takes places as a wet-walled column.
10. Power plant condenser (1) according to one of Claims 1 to 9, characterized in that the deaeration/degasification system is used with converted condensers (1).
11. Power plant condenser (1) according to one of Claims 1 to 9, characterized in that the deaeration/degasification systems is used for the updating and/or partial or complete replacement of the internal air cooler (6).

Images