EP0619466A2 - Steam condenser - Google Patents

Abstract

In a steam condenser, the steam is precipitated onto tubes (pipes) (13) through which cooling water flows and which are combined into separate bundles. Each bundle is subdivided into compartments by support plates arranged perpendicular to the tubes. The tubes of a bundle, which are arranged in rows, enclose a cavity (19) in which there is arranged a cooler (3) for the non-condensable gases. The non-condensable gases pass from the cooler (3) via orifices (6) into a suction channel (4) which is common to all the compartments and extends over the entire length of the tubes (13). There is only one cooler (3), which is immediately adjoined by the suction channel (4), and the through-flow cross-sections of the orifices (6) in the compartments are dimensioned such that given the locally available pressure difference the local, non-condensable mass flow is exhausted. <IMAGE>

Description

Field of the Invention

• wobei jedes Bündel durch senkrecht zu den Rohren angeordneten Stützplatten in Kompartimente unterteilt ist,
• wobei die in Reihen angeordneten Rohre eines Bündels einen Hohlraum umschliessen, in dem ein Kühler für die nicht kondensierbaren Gase angeordnet ist,
• wobei die nicht kondensierbaren Gase aus dem Kühler über Blenden in einen für alle Kompartimente gemeinsamen Saugkanal einströmen, der sich über die ganze Länge der Rohre erstreckt.

The invention relates to a steam condenser in which the steam is deposited on pipes through which cooling water flows and which are combined in separate bundles.

• each bundle being divided into compartments by support plates arranged perpendicular to the tubes,
• the tubes of a bundle arranged in rows enclosing a cavity in which a cooler for the non-condensable gases is arranged,
• the non-condensable gases from the cooler flow through orifices into a suction channel common to all compartments, which extends over the entire length of the tubes.

State of the art

Such a steam condenser is known from CH-PS 423 819 and DE-OS 1 948 073. There, the condenser tubes are arranged in several, so-called sub-bundles in a condenser housing. The steam flows through an exhaust pipe into the condenser housing and is distributed in the room through flow channels (steam entry lanes). The free inflow of steam to the outside tubes of the partial bundles is ensured. The steam then flows through the bundles with little resistance due to the low depth of the tube rows. In order to be able to meet the condition of the steam velocity to be kept sufficiently high in the inflow channels, the partial bundles in the condenser are arranged next to one another in such a way that flow channels arise between them, which in the sectional view appear to be of the same order of magnitude as the partial bundles themselves. Furthermore, the tubes form in the successive rows a permeable enclosure, which preferably represents the same hydraulic resistance throughout.

This known condenser has the advantage that due to the loose arrangement of the sub-bundles, all peripheral tubes of a sub-bundle are well supplied with steam without a noticeable loss of pressure. On the other hand, the requirement for at least approximately the same "wall thickness" or. Resistance of the tube bundle around the cavity a relatively large overall height of the bundle. This results in the excellent suitability of this partial bundle concept for large capacitors, in which a plurality of partial bundles are arranged side by side.

The capacitors working under vacuum require a well-functioning suction system so that incoming, non-condensable gases are always removed from the condensation area will. Cooling tubes that are surrounded or flowed around by these gases mixed with steam are almost completely lost as a condensation surface, which reduces the output.

In addition, the incoming gases cannot keep the vacuum at the lowest possible value. As is known, non-condensable gases - mostly air - already in concentrations of 1% molar fraction, with temperature differences between the wall and the steam core of 4-5 K, a reduction in the heat transfer on the steam side - with quasi-still steam - to 30-40% of that value, which can be achieved with pure steam. The vacuum loss is thus expressed in a lower efficiency of the circulatory system.

In the above-mentioned solution according to DE-OS 1 948 073, an influence arrangement of the pipes is implemented. The sub-bundles are divided into compartments by support plates arranged perpendicular to the tubes. As is known, the condensation capacity along the cooling pipes mainly depends on the local temperature difference between steam and cooling water. The condensation capacity of the first compartments on the cooling water inlet side will then condense more than that of the compartments on the cooling water outlet side. Accordingly, non-condensable gases - proportional to the condensation capacity - will be generated in the "cooler" compartments. In order to take this into account, in the condenser according to DE-OS 1 948 073, which will be described in detail later in connection with FIG. 1, the inert gas enrichment zone is formed in two parts. It consists of a funnel-shaped "pre-air cooler", there called "post-condensation part", and an encapsulated air cooler, which communicates with the pre-air cooler and a downstream suction channel (header) via a double row of evenly distributed cooler inlet orifices or radiator outlet orifices. This encapsulated air cooler is geometrically designed in such a way that the deterioration of the heat transfer on the steam side is partially compensated for by an increase in the speed of the gas phase. Since the encapsulated air cooler adapts to an approximate temperature curve of the cooling water in the neighboring pipes, it therefore ensures that suitable ventilation of the pre-air cooler is approximately proportional to the resulting, non-condensable gases.

Such an encapsulated air cooler construction, however, is not an ideal solution for the different ventilation requirements in the various compartments. Since the exit area from the air cooler is usually too large for uniform extraction, an end wall is arranged between the air cooler and the suction duct in which the radiator outlet covers mentioned above are arranged. The system thus consists of several channels and can only be implemented as a complex sheet metal and welded construction.

Presentation of the invention

The invention is therefore based on the object of providing a capacitor of the type mentioned at the outset which, while maintaining the known advantages of the partial bundle concept, is furthermore distinguished by low production costs.

According to the invention, this is achieved in that only one cooler is provided, to which the suction channel is directly connected, and that the flow cross-sections of the orifices in the compartments are dimensioned such that the local, non-condensable mass flow is sucked off at the locally available pressure difference.

Brief description of the drawing

Fig. 1

ein Teilbündel eines Kondensators mit herausgebrochenen Teilen in Schrägrissdarstellung mit zum Stand der Technik zählendem Luftkühler;

Fig. 2

eine erfindungsgemässe Ausbildung des Luftkühlers in grösserem Massstab.

In the drawing, an embodiment of the invention is shown schematically using a power plant capacitor. It shows:

Fig. 1

a partial bundle of a capacitor with broken-out parts in an oblique view with air cooler belonging to the prior art;

Fig. 2

an inventive design of the air cooler on a larger scale.

In the figures, the same parts are provided with the same reference numerals, the elements which only count towards the prior art being provided with the indication s.

Way of carrying out the invention

The heat exchanger shown is a surface condenser in a rectangular design, as it is suitable for a so-called underfloor arrangement. Parts that are not essential to the invention, such as the condenser neck, condensation chamber, condenser jacket, water chambers, tube sheets, condensate collection vessel, etc. are omitted, but are briefly explained below in connection with the invention.

The steam flows into the condenser neck via an evaporation nozzle with which the condenser is connected to the turbine. The best possible homogeneous flow field is generated therein in order to carry out a clean steam purging of the bundles 20 arranged downstream over their entire length. The condensation space inside the capacitor jacket contains several bundles arranged side by side. One of the objectives of this is that even during plant operation a partial cut-off on the cooling water side can be carried out, for example for the purpose of an inspection of a switched-off bundle on the cooling water side. The independent cooling water supply is expressed by the fact that the water chambers of the condenser are divided into compartments by partitions. A bundle 20 consists of a number of tubes, of which only one cooling tube designated 13s is shown in FIG. 1. At both ends, the cooling tubes are fastened in tube sheets. The water chambers are arranged beyond the tube sheets. The condensate draining from the bundles is collected in a condensate collection vessel and from there it enters the water / steam cycle.

The bundles 20 are designed in such a way that all tubes 13s of the periphery have a good flow of steam without a noticeable loss of pressure. In order to ensure a homogeneous, clean steam flow and in particular to prevent congestion within the bundle, the existing flow paths between the bundles on the one hand and between the outer bundles and their adjacent condenser wall are designed accordingly:

In FIG. 1, the condensation part of the bundle 20, which is only partially visualized by the dotted surface, is designated by 1. By inserting the continuous support plates 5, which serve to support the cooling tubes 13, the sub-bundles are divided into compartments 10.

A cavity 19 is formed inside each bundle 2, in which the vapor enriched with non-condensable gases - hereinafter called air - collects. An air cooler is accommodated in this cavity 19. The steam-air mixture flows through this air cooler, with most of the steam condensing. The rest of the mixture is suctioned off at the cold end.

The air cooler located inside the tube bundle has the effect that the steam-gas mixture is accelerated within the condenser bundle. This improves the situation in that there are no small flow velocities that could impair the heat transfer.

As a further measure, which serves for the uniform application of steam to the bundle, the air cooler is arranged in the interior of the bundle at the level at which the bundle of pressure runs through a relative minimum on both sides of the bundle. In the example shown in Fig. 1, the air cooler is thus in the middle of the bundle. The bundle is designed in such a way that the steam suction into the cavity 19 - taking into account the effective pressure at the pipe periphery and due to the different pipe row thickness - acts homogeneously in the radial direction over all pipes adjacent in the cavity 19. This results in a homogeneous pressure gradient and thus a clear flow direction of the steam and the non-condensable gases towards the air cooler. The upstream cavity 19 has an internal compensation lane 12 which ensures that the air-enriched steam from the core of the front half of the bundle also finds a smooth path to the air cooler.

In operation, the steam condenses on the tubes 13 and the condensate drips off against the condenser bottom. This dripping takes place within the bundle, the condensate coming into contact with steam increasing pressure.

The air cooler has the task of removing the non-condensable gases from the condenser. During this process, the steam losses are to be kept as low as possible. This is achieved by moving the steam / air mixture towards Suction channel is accelerated. The high speed results in good heat transfer, which leads to extensive condensation of the residual steam. In order to accelerate the mixture, the cross section in the direction of flow is increasingly smaller.

1 shows the cooling system mentioned at the outset and known from DE-OS 1 948 073. It consists of the pre-cooler 2s, of which the cooling tube 14s is shown, and the encapsulated air cooler 3s, of which the cooling tube 15s is shown. The space 11s for pressure equalization is arranged between the two. This unthreaded space 11s is also mainly required in order to be able to weld the sheet metal wall 7s separating the air cooler 3s from the precooler 2s to the support plates 5. The panels 9s are arranged in the sheet metal wall 7s. Orifices 6s are also provided in the sheet metal wall 8s provided at the outlet of the cooler 3s, via which the non-condensable gases are drawn off into the suction space 4s. The installation of these throttling points ensures that the pressure difference that is necessary in any case at the beginning and end of the condensation process is mainly reduced in the orifices.

However, achieving controlled flow conditions in the closed air cooler 3s with the aid of the double orifice system is not straightforward. Under certain circumstances, flow-conducting partitions still have to be installed in the air cooler, as shown in FIGS. 2 and 3 of DE-OS 1 948 073. A subsequent change of the panels 9s is no longer possible due to the inaccessibility due to the tubing and any partitions in the cooler 3s. In addition, NH3 corrosion phenomena can occur in the compensation chamber 11s due to the insufficient acceleration of the mixture in the precooler 2s against the air cooler 3s. Depending on the arrangement of the panels 6s, it may also be necessary to drain the air cooler 3s. From the two mentioned above 2 and 3 of DE-OS 1 948 073 it can also be seen that the tubes inside the air cooler are not on the same network as the tubes of the precooler and the condensation zone. This leads to considerable disadvantages when machining the support plates 5 on NC machines.

The invention aims to eliminate all these disadvantages by avoiding an encapsulated cooler. 2, the cooling tubes 15 of the cooler 3 are arranged in a funnel shape for this purpose. The funnel walls 16, which isolate the cooler 3 from the condensation space 1, are connected to one another at an acute angle. At its upper part, the funnel 16 is provided with a cover plate 17, which is placed over the tubes of the cooler toward the cavity 19 and protects them from the steam and condensate flow flowing from top to bottom. This also specifies the direction of flow of the mixture to be cooled, namely from the rear cavity to the front towards the funnel tip. In the area of their connection, these funnel walls simultaneously form the partition 7 to the suction channel 4. In this partition 7, the screens 6 are arranged in the immediate area of the funnel tip. It can be seen from FIG. 2 that the following advantages are associated with this configuration. On the one hand, the mixture to be re-condensed is accelerated up to the entrance of the aperture. On the other hand, it can be seen that only one row of pipes has to remain untubed for the funnel to be welded to the support plates.

The non-condensable gases are sucked off via the orifices 6 into the channel 4, from which they are led out of the condenser in the longitudinal direction. In this case, the suction line 4 penetrates one of the tube sheets (not shown) and the corresponding water chamber.

These diaphragms 6, which are attached in the area of the youngest point of the funnel, represent the physical separation of the condensation chamber 1 from the suction channel 4. They are distributed several times over the entire length of the condenser and, by generating a pressure loss, cause the suction effect to be homogeneous in all compartments 10 of the condenser. For this purpose, their flow cross-section is dimensioned so that the different pressure distribution in the compartments along the condenser length is taken into account. The different cross-sectional requirements per compartment can be covered by appropriate arrangement of a plurality of bores with different diameters and / or different pitches. Orifice diameter and orifice spacing should be selected so that the local, non-condensable mass flow is extracted at the locally available pressure difference.

Compared with the solution belonging to the prior art, it can be seen from FIG. 2 that, on the one hand, considerably less sheet metal is required and consequently less welding work is required, and on the other hand a subsequent modification of the panels 6 is made possible by simply removing the rear wall of the suction channel 4.

REFERENCE SIGN LIST

1

Condensation part

2s

Precooler

3, 3s

cooler

4, 4s

Suction line

5

Support plate

6, 6s

cover

7, 7s

partition wall

8s

Sheet metal wall

9s

cover

10th

Compartment

11s

Compensation room

12,

Compensation alley

13, 13s

Cooling pipe of the condensation part 1

14s

Pre-cooler cooling pipe 2s

15, 15s

Cooling pipe of the cooler

16

Funnel wall

17th

Cover plate

18th

19th

cavity

20th

Sub-bundle

Claims (1)

Steam condenser in which the steam is deposited on pipes (13) through which cooling water flows and which are combined in separate bundles (20), - Each bundle being divided into compartments (10) by support plates (5) arranged perpendicular to the tubes, - The tubes of a bundle arranged in rows enclose a cavity (19) in which a cooler (3) for the non-condensable gases is arranged, - The non-condensable gases from the cooler (3) flow through orifices (6) into a suction channel (4) common to all compartments (10), which extends over the entire length of the tubes (13), characterized, - that only one cooler (3) is provided, to which the suction channel (4) is directly connected, - And that the flow cross-sections of the orifices (6) in the compartments (10) are dimensioned so that the local, non-condensable mass flow is extracted at the locally available pressure difference.

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