JPS5812915A - Corrosion protective device for feedwater heater by drain - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water supply system 1 of a power generation steam turbine; it relates to the prevention of erosion of the inner surface of a container of a feed water heater installed therein.

Conventionally, in the feed water heater of an atomic coupler, steam with a high humidity level of 1°C and a large amount of condensate flowed in, resulting in frequent thinning due to erosion on the inner surface of the container and internal structures at the steam inlet and drain inlet. There is.

The steam inlet of the feedwater heater (4) is a two-phase flow and has a fairly high velocity of 40 to 100 V-.

In this steam 1: Contained fine condensate also flows in at a speed close to steam C and is scattered inside the container, and the impact causes erosion of the inner surface of the container near the steam inlet. Also, the amount of dray flowing in at the drain inlet is 50J! In some cases, it flows in at a speed of about 1/18, and the inner surface of the container near it is thinned due to the scattering of the drain inside. Further, such a large amount of scattered fine particles of drain are accelerated by the steam flow and collide with the protrusions C of other internal structures at a considerable speed, causing erosion. Strictly speaking, this problem refers to erosion and corrosion.

In general thermal power plants, carbon steel materials are used for condensate, water supply, and various equipment installed in the system, but since the material is weak against corrosion, PR in the water supply is used to inject chemical substances into the water supply. Secondly, the occurrence of corrosion is controlled at ζ: 9.0 to 9.5. However, in an atomic couplant, the injection of chemical substances is prohibited in order to prevent contamination within the system due to radioactive C2 of chemical substances.Therefore, the water supplied within the system is pure water with a %PR of about 7, and iron-based materials , the environment is conducive to a certain degree of corrosion. Furthermore, the steam and drain in the feedwater heater are in a temperature range of 150° C. to 200° C., which is a condition that tends to promote corrosion. Therefore, the vessel and some internal structures of the feedwater heater of the atomic coupler are made of Or-MO steel. but,
The protective film formed on the surface is dominated by an iron-based oxide film, and although it is accompanied by a certain degree of corrosion, it resists the impact of condensate (C).
: More destroyed. Further, once the protective film is formed, the corrosion and the destructive effects caused by the impact of the drain are repeated again, and the erosion progresses over time. Considering the damage tendency inside the container, there is no doubt that the erosion effect caused by the collision of drains is the dominant factor that significantly accelerates wall thinning in such p-joon erosion phenomenon 1.・ Figure 1 shows a schematic diagram of the vessel (hereinafter referred to as the main body) on the T-ve charging side of the atomic couplant (binary feed water heater). The steam flows into the heating tube bundle, collides with the impingement plate 3 provided to prevent erosion of the heating tubes, changes direction, flows along the main body shell 114 on the steam inlet side, and flows into the heating tube bundle for heat exchange. At this time, - the condensate 5 in the steam collides with the impingement plate 3 at a speed close to the speed of the incoming steam, and the minute condensate that changes direction and is scattered loses the kinetic energy of the inflow by a certain degree. While being held, it collides with the inner surface part 4a of the body shell near the steam entry port.Erosion occurs at this part C.The impingement plate 3 has the harshest conditions for mechanical and raw 9s C2, so it is not corrosion resistant. Because superior austenitic stainless steel is used, there is little damage.Also, the drain flowing in through the drain inlet port 6 collides with the impingement plate 7 installed directly below it, and flows into the tube bundle. Since the flow velocity is quite high, it is scattered by the impingement 3, and the inner surface 3 of the neighbor vessel of the drain input port 6
bζ: Collisions and causes erosion at this location.

Furthermore, 6-1, these scattered fine condensates become steam flowing through the condensate inlet port 6 and the main body wall 4! 1' flow (2, -) is carried and collides with the protrusion of the support plate 8 supporting the tube bundle, eroding this part. In this way, the workpiece that occurs inside the main body shell is impingement plate. This erosion occurs due to the collision of particulate condensate with a certain degree of kinetic energy scattered by the steam flow, which is then accelerated again by the steam flow and collides with other protrusions.Such erosion is caused by large particles that impede the functionality of the equipment. This can lead to problems and significantly reduce the reliability of the equipment.One way to prevent such erosion is to use corrosion-resistant frame materials, but the fundamental C : C2 is to prevent drainage from scattering.

The present invention has been made with the above in mind:
The purpose of this is to place an impingement plate, which has the function of absorbing the kinetic energy of inflowing condensate and preventing it from scattering, directly below the steam inlet port and below the condensate inlet to prevent the following. Therefore, it is intended to provide a drain corrosion prevention device for a feed water heater that is highly reliable and can be used in practical use.One embodiment of the present invention will be described below with reference to the drawings.Figure 2 shows the present invention. This figure shows the details of the impingement plate 3 by Cyu, and the impingement plate 3 has a conventional flat plate part 9 with a size that takes into account the spread of steam flowing in from the steam input six seats 1&, and a steam and drain plate. It consists of 10% gilt copper 11 double-attached on the collision side, a welded part 12 that connects the wire mesh to the welding surface S''r, and a fixing part 13 for fixing it on the tube bundle. ,
All the parts constituting the impingement plate according to the second method are made of austenitic stainless steel.The impingement plate according to the present invention has a stay pipe directly below the steam inlet port and drain inlet port that fixes the pipe bundle as before. 14 Top I: Screws are fixed with T1-shaped hend 0 The reason for installing a double wire mesh on the conventional impingement plate is this wire mesh (-) When fine condensate collides with the impingement plate, the bottom of the wire mesh (: water filter This is because this water filter collects the kinetic energy of the condensate that flows in one after another.General (:
Cavity erosion and drain erosion have characteristics as shown in Figure 31. At the beginning of erosion, the material surface is smooth, so the collision drain slides and bounces off, and re-erosion does not progress. This is called the incubation period 15. The second stage is the acceleration stage 16, in which the surface roughness of the material becomes rougher to some extent compared to the initial stage of erosion. When the surface becomes rough in this way, erosion is significantly accelerated. However, at a certain point in time, a decay period 17c begins in which the degree of erosion slows down. This is because the surface of the material becomes rough due to erosion, resulting in significant unevenness. This is because when the unevenness becomes severe, a water filter is formed in this portion, and the impact pressure at the time of crushing the middle part or the collision energy of the drain is absorbed by the water filter. A similar phenomenon occurs in the stable phase 18 of the IJ4 stage, and erosion does not progress at an accelerated pace. The present invention takes into account this phenomenon and is based on the idea of using a water filter to absorb the splashing caused by the collision of condensate occurring on the surface of the impingement. Therefore, in order to form a surface condition corresponding to the unevenness C of the material, if a wire mesh is placed over the conventional impingement plate and a water filter is formed, the kinetic energy of the inflow drain will be absorbed and scattered. Decrease. Furthermore, C2: The reason why the wire mesh is installed twice is that if the condensate whose kinetic energy is absorbed by the water filter bounces back at a short range, most of it will be captured by the front wire mesh.

The fourth package shows the situation of condensate scattering on the impingement according to the present invention. As a result, the scattering energy decreases and the bounce distance becomes shorter.
: Most of this scattered fine drain particles collide with the wire mesh on the 2° front side and are scattered again to the inner wire mesh side. The energy is absorbed by the water filter again and the scattering range becomes shorter. However,.

As a result, the amount of fine condensate flying out from the wire mesh on the front side decreases, and its kinetic energy becomes significantly smaller. Therefore, erosion of the inner surface of the main body near the steam inlet and the drain inlet is significantly reduced. Furthermore, since most of the condensate is captured on the wire mesh, the amount of condensate that collides with other protrusions carried by the steam flow is also reduced, so erosion in these areas is also significantly reduced.

As is clear from the above description, the feed water heater equipped with the impingement plate having the structure of the present invention has an excellent effect on erosion prevention.

[Brief explanation of drawings]

Figure 1 is a structural diagram of a conventional feed water heater, -2vA is a diagram showing an embodiment of the present invention, Figure 3 is a graph showing the degree of corrosion of component equipment due to drain C, Figure 4 is an impingement plate. It is a figure which shows the scattering situation of the drain in the upper part. la... Steam account 3... Impingement plate 10.
11...Wire mesh 19...Water filter Figure 2 Figure 3 Time Figure 4

Claims (1)

[Claims] A drain corrosion prevention device for a feed water heater, characterized in that: