JPS6248762B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a feed water heater for a steam turbine for thermal or nuclear power plants.

The heat exchange section of the feedwater heating section is often made by combining a condensing zone and a drain cooler zone.

The condensing zone described above is a part that heats the feed water by giving the latent heat of the heating steam to the feed water, and is the main part of the feed water heater. In addition, a despa heater zone may be installed for heating the feed water to a saturation temperature or higher using steam with a high degree of superheating.

The above-mentioned drain cooler zone provides the water supply with the heat of the drain at the saturation temperature.
It is used to raise the temperature of the water supply and cool the drain to prevent flushing within the drain piping, and its importance has increased in recent years as thermal and nuclear power plants have become larger. The proportion of the size of the feedwater heater in the body is also increasing.

In other words, in the feedwater heaters on the medium and low pressure sides, the conditions for the steam supplied into the fuselage become close to the saturation temperature at the pressure inside the fuselage, and in addition, the amount of condensate flowing in from the steam equipment on the high pressure side increases. Therefore, there is a trend to increase the heat transfer area of the drain cooler zone in order to recover the amount of heat. For this reason, the length of the drain cooler zone now exceeds 1/2 of the fuselage length in many cases.

As mentioned above, as the length of the drain cooler zone increases, it becomes difficult to discharge non-condensable gas in the part located above the drain cooler zone in the condensing zone, which is the main part of the feed water heater. The quality of the discharge of this non-condensable gas has come to significantly affect the performance of the feed water heater. Next, the technical problems will be briefly explained.

FIG. 1 shows an example of a conventionally commonly used feed water heater, FIG. 2 is a sectional view thereof, and FIG. 3 is a sectional view thereof.

The feed water heater generally includes a hollow cylindrical body 9 having both spherical end faces, and a water chamber 1 is formed by partitioning the vicinity of one end with a tube plate 4. The supply water flows into the water chamber 1 from the water supply inlet pipe holder 2 as shown by arrow A, passes through U-shaped heat transfer tubes 5, 5 fixed through the tube plate 4, and flows back and forth in the longitudinal direction within the body 9. The water then flows out from the water supply outlet nozzle 3 in the direction of arrow B.

The internal structure of the fuselage housing the above-mentioned U-shaped heat transfer tubes 5, 5 is on the tube plate 4 side (right side in the figure) and the opposite side (left side) with the cross section Eero near the center of the fuselage 9 as the border. It is broadly divided into.

Part C on the left is the condensing zone,
The U-shaped heat exchanger tube 5 is supported by tube support plates 21, 21. 7 is a tie rod that supports the tube support plates 21, 21 mentioned above.

Each of the tube support plates 21, 21 mentioned above supports the heat exchanger tubes 5 and partitions the inside of the condensing zone into sections 30, 30, 30, . . . .

The upper edges of the tube support plates 21, 21, which are the partition plates, do not reach the ceiling surface of the body 9, and form a longitudinal free flow path 22 in the upper part of the body 9. Therefore, the steam flowing in the direction of the arrow F from the steam inlet nozzle stub 10 is divided into the directions of the arrows G and H, flows downward in each section 30, 30, and comes into contact with the surface of the heat exchanger tube 5 to supply water inside the tube. Heat exchange is performed between the drain 12 and the drain 12, which accumulates at the bottom of the body 9.

The non-condensable gas exhaust main pipe 23 is located along the center line of the fuselage 9 in a part of the condensing zone that is not above the drain cooler zone (area C in Fig. 1).
is installed. The gas component (hereinafter referred to as non-condensable gas) that does not become drain in the incoming steam enters the pipe through the orifice hole 24 bored in the pipe wall of the non-condensable gas exhaust main pipe 23, (See Figure 2) The non-condensable gas is sucked into a deaerator or a condenser (both not shown) through the non-condensable gas guide pipe 25 and discharged outside the body 9. Reference numeral 27 denotes a buffle provided to guide the non-condensable gas to the exhaust main pipe 23, and 28 represents a slit provided in the tube nest of the heat exchanger tubes to guide the non-condensable gas to the exhaust main pipe 23.

The inside of the fuselage 9 on the right side of the Eero surface is divided into upper and lower parts. The upper half area D forms a condensing zone that communicates with the aforementioned condensing zone C, and the heat exchanger tubes 5 are supported by tube support plates 15, 15. The above-mentioned tube support plate 15 is a member similar to the above-mentioned tube support plate 21, but its upper edge reaches the ceiling surface of the body 9, so that steam can freely flow in the longitudinal direction in the upper space of the body 9. is being prevented. Therefore, when a part of the steam sent from the steam inlet nozzle stub 10 flows into this area as shown by arrow J, each section is reversed to the left and right as shown by arrows K, L, and M in a meandering pattern. After flowing, it flows out from the vent seat 26. (See Figure 3) For example, one tube support plate 15l has a cutout on the right side, and an adjacent tube support plate 15m has a cutout on the left side, so that the steam flow is directed by arrows L and M. It meanders while changing direction from side to side. Further, high-temperature drain supplied from the high-pressure side steam equipment is injected from the drain inlet nozzle stub 11 in the direction of arrow N, and heats the water supply in the heat exchanger tubes 5.

A drain cooler zone 13 is provided in the lower right half E of the fuselage 9. The drain 12 mentioned above and the drain flowing down from the drain inlet nozzle 11 are
In this part, the water comes into contact with the heat exchanger tube 5 to heat the supplied water, and is discharged from the drain outlet 14.

In the past, when the length of the drain cooler zone was short compared to the length of the fuselage 9, no particular problems occurred with the above-mentioned structure, but recently, with the increase in the size of power plants, As a result, the length of the drain cooling zone increased to reach 1/2 of the length of the fuselage, as in this example, and the following technical problems arose.

As mentioned above, in the condensing zone which is the upper part of the drain cooler zone, when the steam flow path meanders as shown by the arrows K, L, M..., the ventilation in each section partitioned by the pipe support plates 15, 15 is reduced. It is difficult to do this completely, and the non-condensable gas generated in the D area tends to stay in the bent part of the meandering flow path.

When non-condensable gas remains, not only does the thermal efficiency of the feed water heater decrease, but also corrosive substances (ammonia gas, etc.) in the non-condensable gas are concentrated, promoting corrosion inside the feed water heater.

The present invention has been made in view of the technical trend that requires expansion of the drain cooler zone of a feed water heater, as well as the above-mentioned problems when the drain cooler zone is expanded. The purpose of the present invention is to provide a feed water heater that allows non-condensable gas to be discharged smoothly and sufficiently even when a zone is provided, and that can prevent problems such as a decrease in thermal efficiency and accelerated corrosion due to the accumulation of non-condensable gas. be.

In order to achieve the above object, the present invention provides a direct passage for steam over almost the entire length of the upper space in the fuselage, so that the heated steam flowing into the fuselage is directed to each section partitioned by a tube support plate. A non-condensable gas exhaust main pipe is provided in both the condensing zone above the drain cooler zone and the condensing zone not above the drain cooler zone so that the non-condensable gas can directly flow into the condensing zone. However, since the non-condensable gas exhaust main pipes installed on both sides are under different thermal conditions and are fixed to the partition plate, the thermal expansion and contraction of both non-condensable gas exhaust main pipes is absorbed. In order to achieve this, both of these non-condensable gas exhaust main pipes are arranged on the same axis, are connected via a connecting pipe, and at least one of both non-condensable gas exhaust main pipes is connected to the other through a connecting pipe. Fits slidably into the connecting pipe,
The structure is such that both non-condensable gas exhaust main pipes can approach and separate from each other.

Next, an embodiment of the present invention will be described with reference to FIGS. 4 and 5.

The feed water heater of this embodiment is based on the feed water heater according to the prior art shown in FIG. 1, and the present invention is applied thereto. In this example, members given the same drawing reference numbers as in FIGS. 1 to 3 are the same structural members as in the previous example. However, in this example, one body 9 includes a plurality of steam inlet nozzles 10,
There are 10.

The pipe support plates 51, 51 provided in the condensing zone above the drain cooler zone 13 have their upper edges cut out and are spaced apart from the ceiling surface of the body 9. As a result, a steam flow path is formed in the upper space of the fuselage 9 over almost the entire length of the fuselage, and the steam flowing in from the steam pipe inlet stand 10 is transferred to the pipe support plate 5.
A structure that allows direct flow as shown by arrows P and P into each section partitioned by tube support plates 21 and 21 and tube support plates 51 and 51 without meandering while bypassing tube support plates 21 and 51. It is set as.

The condensing zone in area D, which is the upper part of drain cooler zone 13, is drain cooler zone 1.
A non-condensable gas exhaust main pipe 20 in the longitudinal direction of the body 9 is fixedly installed at a location where it is in contact with the main pipe 3. Figure 1 -
A cross section is shown in FIG. The non-condensable gas exhaust main pipe 20 is communicated with a deaerator or a condenser (both not shown) outside the body 9 via the non-condensable gas guide pipe 18.

Since the present invention provides the steam flow path 22 over almost the entire length in the upper space of the fuselage 9 as described above,
The steam flowing in from the steam inlet pipe stand 10 is transferred to the pipe support plate 2.
It is possible to directly flow into each section divided by 1 and 51. Therefore, the steam can flow smoothly without the risk of creating a stagnant spot due to poor ventilation in the steam flow path in the body 9.

In this example, the above-mentioned drain cooler zone 1
A non-condensable gas exhaust main pipe 20 provided above 3 is disposed on the same axis as the non-condensable gas exhaust main pipe 23 described above, and a connecting sleeve 17 connects the two. FIG. 6 shows an enlarged view of the vicinity of this point. The non-condensable gas exhaust main pipe 20 provided directly above the drain cooler zone 13 by applying the present invention has a drain cooler cover plate 49 surrounding the drain cooler zone.
Since it is located in close proximity to the drain cooler cover plate 49, its lower edge is cut out by the drain cooler cover plate 49, forming a semicylindrical cross-sectional shape R. The connecting sleeve 17 is welded to the non-condensable gas exhaust main pipe 23 and is slidably fitted to the non-condensable gas exhaust main pipe 23 at the fitting surface 16. In this way, the same as the non-condensing discharge main pipe 23
0 through a connecting pipe so that they can be approached and separated, the contact or tension caused by thermal expansion can be released at this part, and deformation and cracking due to thermal stress and thermal distortion can be prevented.

The heat exchange ratio in the feed water heater constructed as above will be described next with reference to FIG. FIG. 7 generally shows the temperature distribution in a tube heat exchanger, with the vertical axis representing the temperature and the horizontal axis representing the position of the tubes.

T is the saturated steam temperature, t ₁ is the feed water temperature at the inlet, t ₂
is the feed water temperature at the outlet.

34 is an entrance section, 35 is an adjacent section, and 45 is an exit section.

Water supply at temperature t ₁ is from section 34 → section 35 → section 3
6, the temperature rises in accordance with the saturation curve while flowing sequentially, and it flows out from the section 45 at a temperature _t2 . Δt ₁ is the temperature difference between the center of the inlet section 34 and the saturated steam, and Δt ₂ is the temperature difference between the center of the outlet section 45 and the saturated steam. in this way,
The temperature difference Δt between the saturated steam and the feed water is different in each section. The heat exchange amount Q (Kcal/hr) in each section is expressed as Q=KSΔt.

K is the heat transmission coefficient (Kcal/m ² hr°C), which can be approximately considered to be a constant value for each section. S is the heat transfer area (m ² ).

Therefore, the amount of heat exchange in each section is approximately proportional to Δt.

In a feed water heater using U-shaped heat exchanger tubes, the feed water inlet and feed water outlet are located above and below the same cross section of the body, so the amount of heat exchange between the upper and lower tubes in these parts is reduced. The difference is maximum.

On the other hand, at a location corresponding to the bottom of the U-shape of the U-shaped heat transfer tube, the difference in heat exchange amount between the upper and lower tube nests becomes minimum, almost zero.

The ratio of heat exchanged at the point where the amount of heat exchanged is maximum (outflow and inlet of the feed water, i.e., the tube plate side in the body) is approximately 1:5 in a nuclear power plant and approximately 1:20 in a thermal power plant. .

FIG. 8 shows a cross section of a portion close to the tube sheet 4 in the above-mentioned embodiment (FIG. 4). At this location, as described above, there is a large difference in the amount of heat exchange between the tube nest 52 in the upper half of the condensing zone and the heat exchange amount of the tube nest in the drain cooler zone 13 in the lower half. The steam flowing from the steam inlet nozzle 10 in the directions of arrows S and S passes through the steam passage 22 formed in the upper space of the body 9 and flows down between the condensing zone tube nests 52 as shown by the arrows U and U. The water supply in the tube nest is heated, and the generated drain flows down to the bottom of the body 9 as shown by arrows W and W. Then, the gas components that have not been condensed (non-condensable gas) are collected in the non-condensable gas collecting section 50 as shown by arrows V and V, and are sucked into the non-condensable gas exhaust main pipe 20.

In this example, the above-mentioned non-condensable gas exhaust main pipe 20
is in close contact with the top surface of the drain cooler cover plate 49, so it is not possible to guide the non-condensable gas by providing a baffle at the Q position diagonally below the non-condensable gas exhaust main pipe 20, but as shown by arrow U. The gas components that have not been liquefied in the flowing down steam are prevented from flowing down by the top surface of the drain cooler cover plate 49, so that they are sucked into the negative pressure in the non-condensable gas discharge main pipe 20 and discharged.

As explained above, the present invention provides a body equipped with piping for introducing heated steam, a plurality of U-shaped heat exchanger tubes provided in the longitudinal direction of the body, and a plurality of U-shaped heat exchanger tubes arranged in a predetermined manner in the longitudinal direction of the body. In the feed water heater, which is equipped with tube support plates supported at intervals of A direct flow path is provided so that the heating steam flowing into the body directly flows into each section partitioned by the tube support plate, and a condensing zone provided in the body is provided with a direct flow path. In the area located above the drain cooler zone,
In addition, non-condensable gas exhaust main pipes are provided in both locations that are not located above the drain cooler zone, and both non-condensable gas exhaust main pipes are connected so that they can approach and separate from each other. Efficiently discharges gas without allowing it to accumulate in the fuselage, reducing heat exchange capacity due to accumulation of non-condensable gas,
It is possible to prevent corrosion inside the fuselage due to accumulation of non-condensable gases, and even when the feed water heater starts operating, changes in operating conditions, and changes in thermal conditions due to stoppage of operation, An excellent practical effect is achieved in that there is no risk of excessive thermal stress or thermal distortion occurring in the non-condensable gas exhaust main tube provided by applying the present invention.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of a conventionally commonly used feed water heater, Fig. 2 is a cross-sectional view of the feed water heater, Fig. 3 is a cross-sectional view of the same, and Fig. 4 is an embodiment of the present invention. 5th longitudinal sectional view of the feed water heater in
The figure is a sectional view of the above embodiment, FIG. 6 is an enlarged sectional view of the vicinity of the non-condensable gas discharge pipe connection sleeve of the above embodiment, and FIG. 7 is a temperature distribution chart of the tubular heat exchanger.
FIG. 8 is a cross-sectional view of a portion near the tube plate in the embodiment of FIG. 4. 5... U-shaped heat exchanger tube, 9... Body, 13...
Drain cooler zone, 15, 21, 51... Pipe support plate, 17... Non-condensable gas discharge main pipe connection sleeve, 20, 23... Non-condensable gas discharge main pipe, 22...
...Direct passage for steam.

Claims (1)

[Claims] 1 A body equipped with piping for introducing heating steam, and a plurality of U provided along the longitudinal direction inside this body.
In the feed water heater, the feed water heater is equipped with a letter-shaped heat transfer tube and a tube support plate that supports the heat transfer tube at a predetermined interval in the longitudinal direction of the body, and a drain cooler zone is provided near the feed water inlet side of the heat transfer tube. A direct passage for steam is provided in the upper part of the fuselage over almost the entire length of the fuselage, so that the heating steam flowing into the fuselage can directly flow into each section partitioned by the tube support plate. In addition, in the condensing zone provided in the fuselage, a non-condensable gas discharge base is provided at both a location above the drain cooler zone and a location not located above the drain cooler zone. The non-condensable gas exhaust main pipe installed at a location above the drain cooler zone and the non-condensable gas exhaust main pipe located at a location not above the drain cooler zone are connected on the same axis. A feed water heater characterized by being arranged in a core shape and connected to each other via connecting pipes so that they can approach and separate from each other.