FIELD OF INVENTION
The present invention relates to a condensate collection tray system for improving deaeration in a steam condenser. More particularly, the invention relates to an arrangement of a tray system to allow collection of water (condensate) due to condensation of steam on the cooling tubes and letting it trickle down into the steam space to get heated resulting liberation of dissolved oxygen from the condensate which in turn improves the deaeration of the steam condenser.
BACKGROUND AND PRIOR ART OF THE INVENTION
In a thermal power plant, a steam condenser which condenses exhaust steam from the turbine comprises of a steam inlet, an exhaust hood, a cooling tube bundle and a hot well for collecting condensate. Steam from turbine enters the condenser through the exhaust hood. Make-up water is sprayed into the condenser through a nozzle located in the exhaust hood. The steam from the exhaust hood gets condensed on the cooling tubes. This water (condensate), as it falls down on the cooling tubes below, gets cooled and absorbs oxygen present in the

surroundings. The condensate gets collected in the hotwell at the bottom of the condenser. For expelling the absorbed oxygen, the condensate needs to be reheated.
Patent no. US2003061814(A1) describes deaeration of makeup water by providing a pipe with spray nozzles in the exhaust hood. These nozzles are arranged counter-current to the flow of steam which heats up the make up water. This arrangement helps deaerating only the makeup water.
Patent No. US4592419(A) discloses an arrangement for deaerating condensate in the hotwell by providing scavenging steam from external source which is introduced in the counter flow direction to the passage of condensate in the hotwell. Here external steam is required for achieving deaeration of the condensate.
Patent No. US4134450(A) describes separated tube bundles with horizontal trays underneath each bundles so that condensate from one bundle does not fall on to the lower bundles. The condensate collected by the trays flows through conduits towards the longitudinal side walls of the condenser and reaches the hotwell by falling along the side walls. Here, the purpose of the trays and conduit system is not to

allow the condensate to fall on to the bottom bundles to avoid its further cooling.
To eliminate dripping of condensed water onto the lower group of cooling tubes, trays are used under Patent No. JP60053783(A) which collect the water condensed on the upper group of cooling tubes. These trays are arranged in between the supporting plates of the condenser and inclined towards one of the supporting plates so that the condensate collected on the trays is made to flow down to hotwell along the supporting plate. In this patent, the purpose of the trays is to avoid large build up of condensate around the tubes due to the condensed water in the upper tubes and thus preventing deterioration of heat transfer in the condenser.
Yet another design of trays in cooling tubes with inclination towards supporting plates is described in Patent No. JP11351763(A) where it is claimed that improvement in deaeration is achieved due to the condensate forming a turbulent flow-down liquid film over the supporting plate and its reheating by the steam fed into the condenser. Here the condensate film thickness is going to be high and accessibility of steam surrounding the film at the supporting plate is very limited as it is covered by cooling tubes. Moreover, the steam

available inside tube bundle is at a lower pressure compared to the exhaust steam and consequently it is at lower saturation temperature. Hence, the deaeration effect is very limited with the design proposed in the patent.
None of the prior art techniques for improving deaeration in condenser directs the condensate collected from bundles of cooling tubes into the exhaust steam space in the condenser where the falling droplets in the free steam space gets deaerated effectively before reaching the hotwell.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a condensate collection tray system for improving deaeration in steam condenser which directs the condensate from the upper bunch of cooling tubes to fall into the steam space.
Another object of the invention is to propose a condensate collection tray system for improving deaeration in steam condenser which allows the condensate to fall in the steam space in small droplets so that

reheating of condensate droplets with the steam is faster and more effective.
Yet another object of the invention is to propose a condensate collection tray system for improving deaeration in steam condenser which is able to restrict condensate fall on the lower cooling tubes so as to avoid cooling of the condensate.
A further object of the invention is to propose a condensate collection tray system for improving deaeration in steam condenser which ensures that the trays provided in the system do not block the steam flow.
A still further object of the invention is to propose a condensate collection tray system for improving deaeration in steam condenser which utilizes the baffle provided to prevent direct steam entry into the air cooling zone as one of the trays with marginal modification.
SUMMARY OF THE INVENTION
With the foregoing objects in view, the present invention provides a novel tray system at appropriate locations within the cooling tube nest

of a steam condenser where the trays are spanned in between the supporting plates with inclination towards the steam spaces for letting the condensate droplets to fall into the steam spaces between the condenser wall and tube nest or that between two tube nests. Appropriately shaped cuts are provided at the ends of the trays to facilitate free flow steam to the cooling tube bundles. Heating of condensate in the steam space liberates dissolved oxygen from the condensate which in turn improves the deaeration of the steam condenser.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 - shows a schematic diagram depicting a steam condenser,
indicating arrangement of trays in the cooling tube bundles according
to the present invention.
Fig.2 - shows the location of trays in between the supporting plates in
a condenser in accordance with the invention.
Fig.3 - shows the condensate flow path from tube bundles to hotwell
in accordance with the invention.
Fig.4 - shows the 3-D view of trays with split ends according to the
invention.

Fig.5 - shows the details of ends of the tray according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
As shown in Fig.1, exhaust steam from steam turbine enters the condenser from the inlet(l), as indicated by arrows the exhaust steam travels down through the exhaust hood (2), surrounds the tube nest consisting of second pass tube bundle (3), first pass tube bundle (4) and the air cooling tube bundle (5) in a typical two pass condenser. Single pass condensers have only the main tube bundle and air cooling tube bundle. The tray system can be used in a single pass as well as a double pass condenser. In case of double pass condenser, more number of trays are provided in first pass compared to that in the second pass as almost two thirds of total exhaust steam is condensed in the first pass. Fig.l shows a double section condenser where it has two tubes nests which are mirror images to each other. It has two side steam spaces/lanes (6) and one central steam space/lane (7). The condensate collection trays (8) placed in the tube nest (3,4,5) are inclined towards the steam spaces (6) between the condenser wall and the tube nest or that between two tubes nests (7) so that condensate

collected on the tray is directed to fall into the steam space so that reheating of condensate droplets with the steam is faster and more effective. The trays are extended into the steam space so that the condensate droplets do not fall on the lower tube bundles. The tray system can be adopted in a single pass as well as double pass steam condensers and also in both single and double section condensers. The tray system can also be used in underslung, axially mounted or side mounted condensers. The baffle (9) which prevents direct entry of steam into air cooling bundle (5) is also used as a tray by giving inclination towards the steam lane (6) and by extending it into the lane. The trays are provided in the system in such a manner that they do not block the steam flow.
As shown in Fig. 1 & 2, a condensate collection tray system (8) located in the cooling tube nest (3, 4, 5) of the condenser connected in between the supporting plates (11) and tube sheet and welded to the supporting plates (11) so that the condensate due to steam condensation on the upper cooling tube bundle gets collected and prevented from falling down on to the lower cooling tube bundles. Steam condenses on the cooling tubes (12) and the condensate trickles down onto the lower tubes. As the condensate from upper rows of tubes travel down to lower tubes, it gets cooled due to

thickening of condensate film on the cooling tubes. Hence, providing intermediate trays helps in stopping further cooling of condensate. Deaeration is based on two scientific principles. The first principle, Henry's Law asserts that gas solubility in a solution decreases as the gas partial pressure above the solution decreases. The second scientific principle that governs deaeration is the relationship between gas solubility and temperature. Gas solubility in a solution decreases as the temperature of the solution rises and approaches zero at saturation temperature. Hence, the solubility of oxygen in condensate increases with cooling of condensate and decreases with heating.
As shown by the arrows in the Fig.3, the condensate collected on the trays flows down towards the steam lanes and falls into the steam space. During the travel of condensate from trays to hotwell (10), it gets heated by the steam which helps in liberation of oxygen.
Fig.4 gives a 3-D view of trays with split ends which are extended beyond the bottom tube bundles so that the drops of condensate do not fall on the lower tube bundles.
Fig.5 shows the details of the ends of a tray. The end converging passages (13) with side walls (14) help in directing the condensate

collected on the tray to the open ends (15) from where the condensate falls as droplets into the steam space. The open areas (16) allow free flow of exhaust steam to lower tube bundles.
A typical power plant condenser with the present invention is expected to reduce the oxygen level (deaeration) in condensate from the present level of 40 ppb to 10 ppb under normal conditions of air leakage. Improved deaeration increases the service life of a thermal power plant. Also, it reduces the necessity of chemical dosing. Promoting heating of condensate to near saturation temperature helps in improving the plant heat rate.
The tray system according to the invention can be adapted to condenser tube nest of any shape. It can be used in underslung, axially mounted or side mounted condensers.

WE CLAIM
1. A condensate collection tray system for improving deaeration in
a steam condenser comprising:
a plurality of trays (8) located in the cooling tube nests (3,4,5) of the condenser, being connected in between the supporting plates (11) and tube sheet;
the said trays being welded to a plurality of supported plates (11) for collecting the condensate falling down from the upper cooling tube bundle and for preventing it from falling down on to the lower cooling tube bundles;
characterised in that the said trays are inclined towards the steam spaces (6,7) between the condenser wall and tube nest or that between two tube nests for directing the condensate collected on the trays (8) to fall into the steam space (6,7) so that reheating of condensate droplets with steam is faster and more effective and extended into the steam space (6,7) for restricting the condensate droplets to fall on the lower tube bundles.
2. A condensate collection tray system as claimed in claim 1,
wherein the trays (8) have end converging passages (13) with
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side walls (14) for directing the condensate collected on the trays (8) to the open ends (15) for allowing the condensate to fall as droplets into the steam space.
3. A condensate collection tray system as claimed in claim 1, wherein the baffle (9) being utilized as one of the trays and provided for preventing direct entry of steam to air cooling bundle (5).
4. A condensate collection tray system as claimed in claim 1, wherein the said tray system can be provided in a single pass as well as a double pass steam condensers.
5. A condensate collection tray system as claimed in claim 1, wherein the said tray system can be adopted to condenser tube nest of any shape.
6. A condensate collection tray system as claimed in claim 1, wherein the said tray system can be adopted in both single and double section condensers.
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7. A condensate collection tray system as claimed in claim 1, wherein the said tray system can be adopted in underslung, axially mounted or side mounted condensers.

A condensate collection tray system for improving deaeration in a steam condenser consists of a plurality of trays (8) located in the cooling tube nests (3, 4, 5) of the condenser and are connected in between the supporting plates and tube sheet and welded to a plurality of supporting plates (11) for collecting the condensate falling down from the upper cooling tube bundle preventing it from falling down on to the lower cooling tube bundles. The trays are inclined towards the steam spaces (6, 7) between the condenser wall and tube nest or between two tube nests for directing the condensate collected on the trays (8) to fall into the steam spaces (6, 7) so that reheating of condensate droplets with steam is faster and more effective and extended into the steam space for restricting the condensate droplets to fall on the lower tube bundles.