JP2002005596A - Method and device for removing vapor-oxidated scale - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily remove a vapor-oxidated scale densely sticking on a metal surface in a short time, with no drainage process such as COD process. SOLUTION: There are provided a first means where a tight fitting force at an interface between a vapor-oxidated scale and a metal surface of base material is decreased by coating or other means, with a processor liquid jetted, a second means to cause a compression or tensile stress on the inside surface of the scale where the sticking force at the interface is decreased by allowing temperature difference between the scale and the base material, and a third means to remove the scale where the fitting to the base material surface is released because of buckling separation and the like under the applied stress. The first, second, and third means are held between a pair of travel means running along a scale formation surface while connected together as one body, for simple and succeeding scale removal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to superheater tubes and reheater tubes for industrial and commercial boilers such as thermal power boilers.
The present invention relates to a method and an apparatus for removing steam oxidation scale generated in tubes such as superheater tubes and heat exchangers provided in ships and incinerators.

[0002]

2. Description of the Related Art Conventionally, a superheater tube and a reheater tube of a boiler are mainly formed of a high-temperature pressure-resistant member such as Cr-Mo steel or SUS steel. When the inner surfaces of these tubes are oxidized by the superheated steam, a steam oxidation scale made of chromium oxide, iron oxide, or the like is formed. For example, in the Kanazu power generation boiler, when these adhered scales peel off, they accumulate on the U vent portion of the superheater tube or the like, and the superheater tube overheats or the peeled scale scatters, causing trouble such as turbine echo. Conventionally, a chemical cleaning method using citric acid has been used as a measure for preventing these obstacles.

However, in such a cleaning method, three times are required for cleaning.
There is a disadvantage that it requires a long time of 0 hour or more. In order to solve such a drawback, Japanese Patent Application Laid-Open No. Sho 62-73003 discloses a method of adding a corrosion inhibitor of about 0.3 to 1.0% to a promoting solution composed of hydroxyacetic acid and formic acid having a pH of 2.5 to 3.2, There is disclosed a technique of removing the steam oxidation scale by forming a suppression mixed acid solution and flowing a heating solution obtained by heating the suppression mixed acid solution to 40 to 90 ° C. in a tube at a rate of staying for about 10 hours.

[0004] However, even in this technique, it takes not only 10 hours to remove the scale, but also because the solution to be removed contains a large amount of dissolved oxides, the subsequent removal of the hydroxy of pH 2.5 to 3.2. The COD treatment must be performed in addition to the neutralization treatment of the accelerating solution composed of acetic acid and formic acid, and the wastewater treatment requires a large cost.

In order to eliminate such a disadvantage, Japanese Patent Application Laid-Open No.
-61529, high-frequency or induction heating is locally applied to the scale attachment portion of the tube wall of a boiler or heat exchanger or the inner wall of a drum to cause a difference in thermal expansion between the metal portion and the scale, thereby reducing the scale. Techniques for peeling and removing have been proposed.

However, the scale has a two-layer structure of a hard and dense chromium-rich layer on the surface of a metal surface and an outer layer which is relatively rich and rich in Fe. It is extremely difficult to peel off only by the difference in thermal expansion.

[0007]

DISCLOSURE OF THE INVENTION In view of the above-mentioned problems in the prior art, the present invention does not require wastewater treatment such as COD treatment, and is a steam oxidation scale that is easily and densely fixed to the surface of a surface in a short time. It is an object of the present invention to provide an invention capable of eliminating the above.

[0008]

According to the first aspect of the present invention, there is provided a method of spraying a treatment liquid and relaxing adhesion at an interface between a steam oxidation scale and a base metal surface by coating or other means. A step of applying a temperature difference between the scale and the base material to generate a compressive or tensile stress on the inner surface of the scale in which the adhesion force at the interface is relaxed, and the adhesion from the base material surface is released by buckling peeling or the like due to the stress application. A steam oxidation scale removal method characterized by comprising a step of removing scale is proposed. The invention according to claim 2 is an invention relating to an apparatus for effectively carrying out the invention, wherein a treatment liquid is sprayed, and the adhesion of the interface between the steam oxidation scale and the base metal surface is reduced by coating or other means. Means for applying a temperature difference between the scale and the base material to generate a compressive or tensile stress on the inner surface of the scale in which the adhesive force at the interface has been alleviated; and And a third means for removing the scale from which the sticking from the material surface has been released.

According to the present invention, thermal (including cold) energy is applied to the scale surface in a state where the adhesive force at the interface between the steam oxidation scale and the base metal surface is reduced by the first means. Since buckling and peeling are performed by generating tensile stress, the scale and the base material are completely separated from each other, and subsequent peeling and removal are easy.

[0010] The treatment liquid by the first means may preferably use, for example, ethylenediamineacetic acid called EDTA or a surfactant in the pH range of a weak acid to a weak alkali. In the case of heating, it is preferable that the treatment liquid by the first means is a liquid that evaporates at the heating temperature of the scale surface (EDTA is around 160 ° C.).

This eliminates or greatly simplifies the treatment liquid wastewater treatment.

The second means may be either rapid heating or rapid cooling as long as a temperature difference at which the scale buckles and separates due to the occurrence of stress can be obtained. Means uses an infrared lamp heater, arc discharge, and laser. In the case of rapid cooling, the latent heat can be effectively used by using a liquefied gas such as liquid nitrogen which evaporates at a low temperature of -70 ° C. or lower.

The third means may include scale suction means,
Preferably, it should include scale crushing and suction means,
In particular, it is preferable to use brushing means or dry ice blast means as the third means.

In particular, the blasting means for dry ice does not require drainage treatment and is easy to remove scale.

According to the present invention, preferably, the first, second and third means are integrally connected to a traveling means which travels along a scale forming surface, and preferably the first, second and third means are scales. It is characterized in that it is sandwiched and integrally connected between a pair of traveling means traveling along the forming surface. This makes scale removal continuous and simplified.

In this case, the integral connection is preferably performed by a flexible body such as a wire. This makes it possible to easily remove scale along a curved pipe or the like.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the drawings. However, unless otherwise specified, dimensions, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the invention, but are merely illustrative examples.

First, the basic procedure of the present invention will be described with reference to FIG. First, in the first procedure, for example, PH5.5 containing ethylenediamineacetic acid called EDTA, a surfactant and the like.
The acid solution adjusted to about 1 is heated to 90 to 95 ° C., and the heat-treated liquid is sprayed on the scale surface, and the pickling spray for reducing the adhesion at the interface between the steam oxidation scale and the base metal surface is performed. . The processing liquid is a liquid that evaporates in the second heating step (E
DTA is preferably set to about 160 ° C.). Next, the surface of the scale is rapidly heated using an infrared lamp heater, arc discharge, and a laser to create a temperature difference between the scale and the base material to generate a compressive stress on the inner surface of the scale where the adhesive force at the interface is reduced, and the compression is performed. Buckling separation is performed by stress. The heating temperature was, as shown in FIG.
Mo steel) and steam oxidation scale (Fe ₃ O ₄ )
When the temperature exceeds 00 ° C., a difference in expansion coefficient occurs, and at 450 to 550 ° C., the difference becomes extremely large. Therefore 300-550 ° C
What is necessary is just to heat the scale surface rapidly so that a temperature difference of a degree occurs. Needless to say, the larger the temperature difference, the larger the difference in expansion rate, so that the steam oxidation scale is more easily peeled off. The scale that has been released from the surface of the base material due to buckling peeling or the like due to the application of the stress is suction-removed while being crushed using brushing means or dry ice blasting means. As a result, the heat at the interface between the steam oxidation scale and the base metal surface is relaxed while the adhesion is relaxed.
Since buckling peeling is performed by applying energy (including cold heat) to the scale surface to generate compressive stress, the scale is completely separated from the base material, and subsequent peeling and removal is easy.

FIGS. 3 and 4 show a scale removing apparatus using the above-mentioned invention. This apparatus is a scale removing apparatus for a high-temperature reheat steam pipe 1 having a pipe inner diameter of 800 mm and a length of 100 m. The steam pipe 1 has an opening 1a as shown in FIG. It is curved in a rectangular shape through the part,
Γ holes 1b used for X-ray transmission inspection are provided on the tube wall at appropriate intervals, and an RH exit shifter 5 is connected to the exit side. In this apparatus, the guide wire 6 drawn out from the lifting device 3 is inserted through the γ hole 1b on the outlet side, drawn out from the pipe inlet side opening 1a and connected to the feeding device 2 side, and the wire 6 is connected to the scale removing device main body. And the traveling device 4 is
While spirally rotating along the guide wire 6, the tube 1
The scale is removed from the inner surface, and the scale removed is collected and collected by a dust collector provided in the feeding device 2 through the main cable 10.

Next, the traveling device will be described with reference to FIG. In the figure, reference numeral 10 denotes a main cable.
CD camera 12, pickling spray unit 13, heating unit 14, removal and recovery unit 15, and rear traveling unit 1
1B, a power cable for supplying power to each unit from a power box 7, a video signal from a CCD camera 12, and a control signal from a remote control box. And a signal cable for transmitting the signal to each unit. The main cable 10 extends to the power supply box 7 as shown in the lower section of FIG. 3, and the signal transmission cable in the cable 10 is connected to the remote box 8,
A predetermined control operation is performed while capturing the video signal from the D camera 12 and displaying the in-tube video on the monitor 9.

On the other hand, the traveling device 4 includes a main cable 1
0, or via a connecting pipe (not shown) capable of flexible movement, the units are integrally connected to each other, and the traveling units 11A, 1
Guide wire 6 while being spirally rotated by the drive of 1B.
Travels spirally along the pipe. In addition, a cross-shaped in-pipe space holding member 16 is provided between the main cables 10.
(Or a connecting pipe), and has a space holding function when the traveling device 4 passes through a curved pipe.

Next, the configuration of each unit will be described. The front and rear traveling units 11A and 11B have a built-in motor that slowly rotates the traveling device 4 to the rear unit 11B at a predetermined cycle while moving in the pipe axis direction by the wire lifted by the lifting device 3. . In the rear traveling unit 11B, a connector (not shown) for rotatably connecting the main cable 10 in the traveling apparatus and the main cable 10 to the power supply box 7 on the downstream side is provided. Without the main cable 10 twisting and rotating on the side
It is ensured that only the traveling device 4 and the main cable in the traveling device connected thereto rotate.

The CCD camera 12 captures an image of the scale immediately after the front traveling unit, so that an operator who is remotely monitoring the monitor 9 can transmit an appropriate control signal to each unit.

The pickling spray unit 13 has a spray nozzle 13a attached to a side surface of a cylindrical body having a built-in processing solution storage tank and a liquid pressure feeding mechanism.
In a, a predetermined processing liquid is sprayed onto the inner surface of the pipe while being spirally rotated integrally with the traveling device 4 to carry out pickling spray for reducing the adhesion at the interface between the steam oxidation scale and the base metal surface.

The heating unit 14 is provided with an arc-shaped infrared lamp heater 14a at symmetrical positions on the side surface of the cylindrical main body. The heating unit 14 rapidly heats the scale surface after the treatment liquid is sprayed, and the scale and the base material are heated. A compressive stress is generated on the inner surface of the scale in which the adhesive force at the interface is relaxed by applying a temperature difference therebetween, and buckling peeling is performed by the compressive stress. The heating temperature is set so that a temperature difference of about 300 to 550 ° C. occurs between the base material and the steam oxidation scale.

The removal / recovery unit 15 is provided with a horn-shaped blast suction unit 15a provided with a dry ice spray unit and a suction nozzle unit on the side surface of a cylindrical body having a dry ice storage unit and a suction unit. . Thereby, it is possible to crush and remove the scale after buckling peeling while crushing the scale by dry ice blasting.

The crushed scale removed by suction is guided to the outside from a suction pipe (not shown) provided in the main cable 10,
The dust is collected by the dust collector 2 shown in FIG.

After removing the scale, the wire is rewound by the feeding device 2 shown in FIG.
Is taken out of the tube, removed from the guide wire 6, and the predetermined operation is completed.

Therefore, according to the present embodiment, the step of relaxing the adhesion at the interface between the steam oxidation scale and the surface of the base metal and reducing the heat energy by simply moving the traveling device through the pipe along the guide wire, And a step of generating compressive stress to perform buckling peeling and a scale peeling removal suction step can be performed continuously, thereby making scale removal continuous and simplified.

In particular, according to the present embodiment, since the integral connection is made by a flexible body such as a wire or a main cable, the scale can be easily removed along a curved pipe or the like.

[0031]

As described above, according to the present invention, thermal (including cold) energy is applied to the scale surface in a state where the adhesive force at the interface between the steam oxidation scale and the base metal surface is relaxed. Alternatively, buckling and peeling occur due to tensile stress, so that the scale and the base material are completely separated and the subsequent peeling and removal are easy, as well as the treatment liquid is substantially eliminated by evaporation, so that drainage treatment is performed. Is unnecessary or greatly simplified.

Further, according to the present invention, the scale removing means is integrally connected to the traveling means running along the scale forming surface, and the scale can be removed while moving. Therefore, the scale removal is made continuous and simplified. In addition, the scale can be easily removed along a curved pipe or the like.

[Brief description of the drawings]

FIG. 1 is an operation diagram showing a basic procedure of the present invention.

FIG. 2 is a graph showing the relationship between the scale and the thermal expansion coefficient of the base material.

FIG. 3 shows a main configuration of a scale removing device according to an embodiment of the present invention.

FIG. 4 shows an overall schematic diagram of the embodiment of FIG.

[Description of Signs] 1 Steam pipe 1b Hole 3 Lifting device 4 Traveling device 6 Guide wire 7 Power supply box 8 Remote box 9 Monitor 10 Main cable 11A, 11B Traveling unit 12 CCD camera 13 Pickling spray unit 14 Heating unit 15 Removal unit

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshio Sao 5-717-1 Fukabori-cho, Nagasaki-shi Mitsubishi Heavy Industries, Ltd. Nagasaki Research Institute Co., Ltd. (72) Inventor Yoshiaki Hirayama 5-717-1 Fukahori-cho, Nagasaki-shi Mitsubishi (72) Inventor Takashi Morimoto 5-717-1 Fukahori-cho, Nagasaki City Mitsubishi Heavy Industries, Ltd.Nagasaki Research Center (72) Inventor Kensaburo Takezoe 5-7-17-1 Fukahori-cho, Nagasaki City Mitsubishi Heavy Industries, Ltd.

Claims (13)

[Claims] 1. A step of spraying a treatment liquid to reduce the adhesion at the interface between the steam oxidation scale and the base metal surface by coating or other means, and applying a temperature difference between the scale and the base material to form an interface. It is characterized by comprising a step of generating a compressive or tensile stress on the inner surface of the scale with reduced adhesion, and a step of removing the scale that has been released from the base material surface due to buckling peeling or the like due to the stress application. Steam oxidation scale removal method. 2. A first means for spraying a treatment liquid to reduce the adhesion at the interface between the steam oxidation scale and the base metal surface by coating or other means, and providing a temperature difference between the scale and the base material. A second means for generating a compressive or tensile stress on the inner surface of the scale in which the adhesive force at the interface has been alleviated, and a third means for removing the scale which has been released from the base material surface due to buckling peeling or the like due to the stress application. And a steam oxidation scale removing device. 3. The treatment liquid according to the first means, wherein the treatment solution is a weak acid
3. The apparatus for removing steam oxidation scale according to claim 2, wherein the treatment liquid is in a pH range of a weak alkali. 4. The steam oxidation scale removing apparatus according to claim 2, wherein when the second means is a rapid heating, the processing liquid by the first means is a liquid that evaporates at a heating temperature of the scale surface. 5. The steam oxidation scale removing apparatus according to claim 2, wherein said second means is means for giving a temperature difference between said scale and said base material by rapid heating or rapid cooling. 6. The steam oxidation scale removing apparatus according to claim 2, wherein when the second means is rapid heating, the second means is an infrared lamp heater, an arc discharge, or a laser. 7. The steam oxidation scale removing apparatus according to claim 2, wherein the second means is a low-temperature evaporated liquefied gas such as liquid nitrogen when the second means is rapid cooling. 8. The steam oxidation scale removing apparatus according to claim 2, wherein the third means includes a scale suction means. 9. The steam oxidation scale removing apparatus according to claim 2, wherein said third means includes means for crushing and sucking scale. 10. The steam oxidation scale removing device according to claim 2, wherein said third means includes dry ice blasting or brushing means. 11. The steam oxidation scale removing apparatus according to claim 2, wherein said first, second and third means are integrally connected to a traveling means traveling along a scale forming surface. . 12. The apparatus according to claim 11, wherein said first, second and third means are sandwiched and integrally connected between a pair of running means running along a scale forming surface.
The steam oxidation scale removing device according to the above. 13. The steam oxidation scale removing device according to claim 11, wherein the integral connection is performed by a flexible body such as a wire.