EP0384200A1 - Steam condenser - Google Patents

Abstract

In a floor-mounted steam condenser, in which the steam is precipitated on tubes (5) through which cooling water flows and which are grouped in separate bundles (2), the tubes (5) of a bundle, which are arranged in rows, enclosing a cavity (13), a cooler (14) for the non-condensable gases is arranged in the cavity (13). <??>The longitudinal extent of the sub-bundles (2) is aligned horizontally, and the sub-bundles are arranged vertically one above the other. The suction effect of the cooler (14) for the non-condensable gases is directed towards a zone below the longitudinal centre line (22) of the individual bundle (2). <IMAGE>

Description

Field of the Invention

The invention relates to a steam condenser for ground-level arrangement with a steam turbine, the steam being deposited on pipes through which cooling water flows and which are combined in separate sub-bundles, and wherein the pipes of a bundle arranged in rows enclose a cavity in which a cooler for the non-condensable gases is arranged ,

State of the art

Such a steam condenser, however for the so-called underfloor arrangement, is known from Swiss Patent No. 423 819. 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. These narrow in the general direction of the flow in such a way that the flow velocity of the steam in these channels remains at least approximately constant. The free inflow of steam to the outside tubes of the partial bundles is ensured. The steam then flows through the bundles with a small resistance due to the low pipe depth. In order to meet the condition of the steam speed to be kept constant in the inflow channels len, the sub-bundles in the condenser are arranged next to each other in such a way that flow channels are created between them, which appear in the sectional view in the same order of magnitude as the sub-bundles themselves. Furthermore, the tubes in the successive rows form a self-contained wall, which is preferably continuous is of the same thickness.

This known condenser has the advantage that due to the loose arrangement of the partial bundles, all peripheral tubes of a partial bundle are well charged with steam without any noticeable pressure loss. On the other hand, the requirement for at least approximately the same "wall thickness" of the tube-shaped sub-bundle around the cavity results in a relatively large overall height of the sub-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. This known solution is less suitable for steam condensers of power plants, in which the condenser and the turbine are located approximately at the same height of the machine house foundation, for example due to a limitation in the height. In such cases, the capacitor can be arranged coaxially with the turbine shaft or laterally along the turbine. Underfloor arrangements are also not possible with watercraft driven by a steam turbine with a shallow draft.

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 by
- that the partial bundles are oriented horizontally in their longitudinal extent,
that several sub-bundles are arranged one above the other in the vertical,
- And that the cooler is formed asymmetrically within the sub-bundle and that its intake cross-section has its center of gravity below the longitudinal center line of the sub-bundle.

The advantages of the invention can be seen in the fact that as a result of the deliberately implemented pressure reduction in the flow-through alleys at the level of the air cooler on both sides of the respective bundle, the steam-side pressure drop across the bundle is approximately constant, so that there is a homogeneous pressure gradient in the direction of the cooler . With this measure, good steam flushing through the bundle is achieved. After passing through the maximum speed, the steam in the alleys is decelerated to zero with pressure recovery at the level of the condensate collector. This causes an increase in the saturation temperature of the steam and thus a regression of the condensate supercooling that has taken place and the oxygen concentration in the condensate. The fact that, due to the selected flow guidance, the accumulation only occurs at the lower end of the bundle, accumulations of non-condensable gases in the bundle lanes themselves are avoided.

Due to the regenerative character of this bundle type and the targeted arrangement of the air cooler, a specific condensation capacity is to be expected, which is at least 10% above the model defined by the "Heat Exchanger Institute Standards".

In addition, other advantages can be seen in the simple and fast manufacture of the foundation and in short commissioning times. In particular, there is the possibility of dispensing with the previous expansion elements and the capacitor to be connected directly to the exhaust steam casing of the turbine and to be supported by simple sliding shoes.

It is expedient if the tubes of the cooler are provided in the cavity of the bundle with a cover plate, which is also designed as a closed suction channel that communicates with the cooler zone via panels. The multifunctional cover plate protects the cooler pipes from the condensate running down.

To lead out of the condenser, it is recommended that the steam-air mixture flowing from the cooler into the suction channel be sucked out of the channel via at least one suction line penetrating each bundle, for which purpose a resp. two rows of pipes in the otherwise closed jacket are missing and replaced by blind pipes. These dummy pipes, which act as vapor barriers, prevent the steam from flowing directly into the air coolers.

A similar shielding is known from the previously mentioned CH-PS 423 819. However, there is a closed casing, which is an obstacle to flow in the vertical direction, in particular for the condensate dripping down.

Brief description of the drawing

• Fig. 1 und 2 eine skizzenhafte Vorderansicht und Draufsicht einer Niederdruckturbine mitsamt Kondensator;
• Fig.3 einen Querschnitt durch den Kondensator;
• Fig.4 einen Querschnitt durch ein Teilbündel;
• Fig.5 einen Querschnitt durch einen Kühler.

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

• 1 and 2 a sketchy front view and top view of a low-pressure turbine together with the condenser;
• 3 shows a cross section through the capacitor;
• 4 shows a cross section through a sub-bundle;
• 5 shows a cross section through a cooler.

The heat exchanger shown is a surface condenser in a rectangular design, as it is suitable for the so-called "on floor" arrangement. As a rule, such capacitors have useful power ranges of <300 MWe.

Way of carrying out the invention

The steam flows into the condenser neck 1 via an evaporation nozzle 10, 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 2 arranged downstream over their entire length.

The condensation space inside the condenser jacket contains four separate bundles 2. This has the aim, among other things, that a partial shutdown on the cooling water side can also be carried out during system operation, for example for the purpose of an inspection of a shutdown bundle on the cooling water side. The independent application of cooling water is expressed in that the water chambers 7 (FIG. 2) are divided into compartments by horizontal partition walls (not shown).

The bundles consist of a number of tubes 5, which are fastened at their two ends in tube plates 6. Beyond the tube sheets, the water chambers 7 are arranged. The condensate flowing off from the bundles 2 is collected in the condensate collecting vessel 12 and from there it reaches the water / steam circuit, not shown.

According to FIG. 3, a cavity 13 is formed in the interior of each bundle 2, in which the cavity contains gases that cannot be condensed - hereinafter called air - collects enriched steam. An air cooler 14 is accommodated in this cavity 13. 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.

Apart from the horizontal alignment, sub-group capacitors are known so far. It should be noted that the air cooler located inside the tube bundle has the effect of accelerating the steam-gas mixture within the condenser bundle. This improves the situation in that there are no low flow velocities that could impair the heat transfer.

Based on the specified external shape of the capacitor - in this case a cuboidal capacitor shell - the shape of the four bundles 2 is adapted so that the following goals are achieved:
- Good use of the temperature gradient
- Small pressure drop in the tube bundle despite the high packing density of the tubing
- No stagnant air accumulation in the steam lanes and the bundles
- No undercooling of the condensate
- Good degassing of the condensate.

For this purpose, the bundles are designed in such a way that all pipes in the periphery have a good flow of steam without noticeable pressure loss. In order to ensure a homogeneous, clean steam flow and in particular to exclude congestion within the bundle, the existing flow paths between the four bundles 2 on the one hand and between the outer bundles and their adjacent condenser wall are designed as follows:

First, it is assumed that a somewhat homogeneous flow field prevails over the entire outflow cross section of the condenser neck 1. The predominant first part of the flow path between the beginning and end of the bundle is designed to be convergent. The flowing steam experiences a spatial acceleration with a corresponding decrease in the static pressure. This is approximately homogeneous on both sides of the bundle. When narrowing the channel on both sides of the bundle, account must be taken of the fact that due to the condensation, the steam mass flow becomes increasingly smaller.

After reaching the maximum specified speed, the steam is now decelerated to zero speed with a simultaneous pressure recovery. This is achieved by making the second part of the flow path divergent. It should also be noted here that the channel expansion does not have to be optically recognizable due to the increasing decrease in the mass flow. It is important that the residual steam flowing towards the condenser bottom 8 generates a dynamic pressure there. This deflects the steam and also supplies the lower parts of the bundle. The increase in temperature caused by the dynamic pressure benefits the condensate flowing down from pipe to pipe by heating up again if it has cooled below the saturation temperature. This ensures two advantages: There are no thermodynamic losses due to condensate hypothermia and the oxygen content of the condensate is reduced to a minimum.

As a further measure, which serves the uniform application of steam to the bundle, the air cooler 14 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, the air cooler is therefore located in the rear half of the sub-bundle. The bundle is designed so that the vapor intake into the hollow Room 13 - taking into account the effective pressure at the pipe periphery and due to the different pipe row thickness - acts homogeneously in the radial direction across all pipes in the cavity 13. This results in a homogeneous pressure gradient and thus a clear direction of flow of the steam and the non-condensable gases in the direction of the air cooler 14. The cavity 13 opens upstream into a compensation lane 16 inside the bundle, which also ensures that the air-enriched steam from the core of the front half the bundle finds a smooth way to the air cooler.

In operation, the steam condenses on the tubes 5 and the condensate drips off against condensate collecting plates 11. This dripping takes place within the bundle, the condensate coming into contact with steam increasing pressure. These sheets 11 are attached in order to avoid the influence of the condensate flowing down on the bundles underneath. Between the top and second top and between the bottom and the second bottom bundles, these sheets extend from the level of the air cooler 14 to the area of the condenser bottom 8. Between the middle bundles, the sheet 11 extends to the upper edge of the bundles. The economical use of condensate collecting plates is due to the fact that they simultaneously slow down the steam flow in the steam supply lane and thereby prevent pressure regeneration. The sheets cover the bundles, but in any case leave enough free space for pressure equalization and for pressure regeneration by stagnation of the residual steam speed at the end of the condensation path, i.e. impossible in the region of the capacitor bottom 8. The resulting steam cushion causes any condensate subcooling to regress and the residual degassing of the condensate, which is finely divided at this point.

The entire condenser shell assembly, ie housing, as well as partial bundles and condensate collecting plates, is in the longitudinal direction of the pipe slightly inclined about the turbine axis 24 in order to promote the rapid drainage of the condensate.

As can be seen in particular from FIGS. 4 and 5, the air coolers within the partial bundles are asymmetrical in shape and of an ascentric position within the cavity 13. In contrast to the already mentioned underfloor arrangement of the condenser, the bundles 2 are subjected to a highly asymmetrical load when installed horizontally, since gravity and the inertial force of the vapor velocity are almost perpendicular to each other. However, this asymmetry mainly relates to the condensate load in the bundle, which also leads to an asymmetrical localization of the pressure minimum in the pipe structure with regard to the geometrical bundle contours.

The location of the minimum pressure dictates the location of the air cooler as it is the location of the accumulation of non-condensable gases. The condensate raining down from above increases the steam-side pressure loss in the lower half of the bundle and thus causes the pressure minimum to shift downwards. The air cooler is therefore configured and arranged in such a way that it takes account of the asymmetry mentioned. The air is drawn in below the longitudinal center line 22 of the bundle due to the chosen cooler configuration.

The air cooler 14 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 in that the steam / air mixture is accelerated in the direction of the suction duct 17. 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, as can be seen in FIG. 5. The air is sucked off through orifices 18 into the channel 17. These covers, which are attached to the youngest part of the radiator cover are the physical separation of the condensation space from the suction channel. They are distributed several times over the entire length of the pipe and, by creating a pressure loss, ensure that the suction effect is homogeneous in all compartments of the condenser.

Part of the wall of the suction channel 17 is also designed as a funnel-shaped cover plate 19. This sheet is placed over the pipes of the cooler and protects them from the steam and condensate flow flowing from top to bottom. This also specifies the direction of entry of the mixture to be cooled, namely from the back to the front towards the screens 18.

The drainage of the suction channel 17 takes place through holes 23 arranged several times in the longitudinal direction of the channel at the lowest point of the channel.

In order to guide the air from the suction duct 17 to the suction apparatus (not shown), a corresponding number of tubes 5 are left out of the bundles 2. Depending on the size and staggering of the tubes 5, this involves omitting either one or two rows of tubes. A plurality of suction lines 20 penetrating the bundle upward are led out through this recess. Parallel to the bundle, these suction lines are led to the condenser bottom 8, where they open into a collecting line 15 leading to the suction device.

The free space created by the omission of the pipes is filled with vapor barriers. The primary goal of these is to prevent steam bypass. In the present case, these are dummy pipes which do not prevent the vertical exchange of steam or condensate. In the direction of the steam lane / cooler, they form a flow obstacle that should have the same pressure loss as the original pipe. In addition, these blind pipes can also be used as support anchors between the pipe support plates, not shown.

Of course, the invention is not limited to the exemplary embodiment shown and described. For example, longitudinal, staggered, baffle-like sheets could be used as vapor barriers instead of the dummy pipes. The vapor barriers could also be dispensed with entirely if the non-condensable gases are led out of the condenser in the longitudinal direction of the tube instead of across the bundle. In this case, the suction channel, respectively. the suction line connected to it penetrate one of the two tube plates 6 and the corresponding water chamber 7. Finally, the condenser can of course also be divided into two and arranged on both sides of the turbine. Likewise, it can be set up in the extension of the turbine axis.

REFERENCE SIGN LIST

• 1 condenser neck
• 2 sub-bundles
• 3 turbine
• 4 capacitor jacket
• 5 pipe
• 6 tube plate
• 7 water chamber
• 8 capacitor bottom
• 9 foundation
• 10 evaporation nozzle
• 11 Condensate collecting plate
• 12 condensate collector
• 13 cavity
• 14 air cooler
• 15 manifold
• 16 compensation alley
• 17 suction channel
• 18 aperture
• 19 cover plate
• 20 suction line
• 22 longitudinal center line of 2
• 23 drainage hole in 17
• 24 turbine axis

Claims (5)

1. steam condenser for ground-level arrangement with a steam turbine, the steam being deposited on pipes (5), through which cooling water flows and which are combined in separate sub-bundles (2), and wherein the pipes of a bundle arranged in rows enclose a cavity (13) in which a cooler (14) is arranged for the non-condensable gases,
characterized,
- That the partial bundles (2) are horizontally directed in their longitudinal extent,
that several sub-bundles are arranged one above the other in the vertical,
- And that the cooler (14) is asymmetrical within the sub-bundle and that its intake cross-section has its center of gravity below the longitudinal center line (22) of the sub-bundle. 2. Steam condenser according to claim 1, characterized in that the tubes of the cooler (14) in the cavity (13) of the bundle (2) are provided with a cover plate (19) which is designed as a closed suction channel (17), the latter with the coldest cooler zone communicates via panels (18). 3. Steam condenser according to claim 2, characterized in that the steam-air mixture flowing into the suction channel from the cooler is withdrawn from the channel via at least one suction line (20) penetrating the bundle, for which purpose within the sub-bundle a two rows of pipes in the otherwise closed jacket are missing and replaced by blind pipes (21). 4. Steam condenser according to claim 1, characterized in that a horizontally oriented condensate collecting plate (11) is arranged between two sub-bundles (2), which extends at least from the plane of the cooler (14) to the region of the condenser bottom (8). 5. Steam condenser according to claim 1, characterized in that the structural unit condenser shell / partial bundle / condensate collecting plates is slightly inclined in the longitudinal direction of the pipe relative to the turbine axis (24).

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