JP2002090286A - Equipment and method for evaluating corrosion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an equipment and a method for evaluating corrosion in the boiler piping or the pressure piping of a large scale plant, a nuclear reactor, and the like. SOLUTION: The equipment for evaluating corrosion comprises a rotator 13 fixed with a plurality of test pieces 12 in an autoclave 11, means for rotating the rotator, and means 15 for supplying water 14 into the autoclave 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for evaluating corrosion in boiler piping and pressure piping of large plants, nuclear reactors and the like.

[0002]

2. Description of the Related Art Components such as pipes of power plants, chemical plants, electronic power plants, and the like cause corrosion due to long-term use. Therefore, it is urgently necessary to elucidate the corrosion phenomenon. In particular,
Due to the action of high-temperature water, the corrosion of the components is different from that at normal temperature, and it is important to understand the state of corrosion. In particular, in order to evaluate the properties of the oxide (film) scale adhering to the inner surface of the tube under high-temperature and high-pressure conditions, it is proposed to create and evaluate various test pieces under the same conditions as those of the actual machine. Have been.

FIGS. 10 to 13 show an example of a conventional method for producing a test piece. Conventional oxidation scale generators are:
A boiler tube 01 of the same size and material as the tube used in the actual machine is used.
2. A scale is generated based on the water quality conditions (temperature, pressure, water quality, etc.) at the time of actual operation, and thereafter, as shown in FIG. We are observing.

Further, as shown in FIG. 12, after halving, in order to observe the cross-sectional shape, it is embedded in a resin 03, the surface is polished, and a microscope or X-ray observation is performed to evaluate corrosion. Is going.

Conventionally, a large amount of test water is supplied (3 t /
H) and equipment such as large pumps and heaters and their associated equipment to establish conditions of high flow rates (≒ 4 m / s)
For example, there is a problem that maintenance costs such as required power and labor costs are increased.

Further, since the scale is formed in the tube, it is impossible to confirm the adhesion state during the scale generation, and only the sample after a certain time has elapsed can be evaluated.

Further, at the time of the evaluation, it is necessary to take out the tube and divide it in half, so that there is a problem that the scale cannot be generated again. Therefore, conventionally, there is a problem that various states in the scale growth process cannot be evaluated.

In addition, when evaluating the adhesion of the scale using various materials, it is necessary to use the above-described large-scale apparatus each time, and there is a problem that it takes time and effort.

SUMMARY OF THE INVENTION In view of the circumstances described above, an object of the present invention is to provide a corrosion evaluation method and apparatus for evaluating, for example, corrosion in boiler piping and pressure piping.

[0010]

According to a first aspect of the present invention, there is provided a scale generating apparatus for solving the above-mentioned problems, wherein a rotating body having a plurality of test pieces attached thereto in an autoclave and the rotating body are rotated. Means and water supply means for supplying water into the autoclave.

[0011] The invention of claim 2 is characterized in that, in claim 1, a viewing window is provided in the autoclave.

According to a third aspect of the present invention, in the first aspect, a deaeration means for removing oxygen in the supply water to the supply line of the supply water, and an oxygen gas having a predetermined amount of concentration in the deaerated supply water. And an oxygen supply device for supplying oxygen.

According to a fourth aspect of the present invention, there is provided a corrosion evaluation apparatus including the scale generating apparatus according to any one of the first to third aspects, and a platinum electrode provided at a position facing the test piece. It is characterized by.

According to a fifth aspect of the present invention, in the fourth aspect, a reference electrode is provided.

According to a sixth aspect of the present invention, there is provided a scale producing method, wherein a rotating body having a plurality of test pieces attached thereto is rotated in an autoclave, and water is supplied into the autoclave.
An oxide scale is formed on the test piece surface.

According to a seventh aspect of the present invention, there is provided a corrosion evaluation method, wherein a rotating body having a plurality of test pieces mounted thereon is rotated in an autoclave, water is supplied into the autoclave, and an oxide scale is generated on the test piece surface. In this state, electrochemical evaluation is performed.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

[First Embodiment] FIG. 1 is a schematic diagram of a scale generating apparatus according to the present embodiment, and FIG. 2 is a schematic diagram of a scale generating system using the apparatus. The scale generating apparatus according to the present embodiment includes a rotating body 13 having a plurality of test pieces 12 attached thereto in an autoclave 11, means for rotating the rotating body 13 (not shown), and water supplied into the autoclave 11. A water supply means 15 for supplying the water 14 is provided. In FIG. 1, reference numeral 16 denotes a stirring shaft of stirring means for stirring water in the autoclave 11, 17 denotes superheating means, and 18 denotes discharged water.

As shown in FIG. 2, the water supply means 15 is interposed in a circulation line 21 for supplying water, and converts the supply water 14 supplied to the autoclave 11 into pure water, for example, pure water such as ion exchange resin. A device 22, a deaeration tank 23 for completely removing O ₂ in the feed water, a high-pressure pump 24 for feeding the feed water 14 to the autoclave 11 at a predetermined pressure, and an oxygen for adjusting the pH and the O ₂ concentration in the feed water. The supply device 25 is provided. In addition, as shown in FIG.
An electric conductivity measuring device 27, a dissolved oxygen measuring device 28, and a pH meter 29 are interposed to perform various measurements.

As shown in FIG. 3, the oxygen supply device 25 includes a tank 32 provided in a thermostat 30 and containing an ammonia water 31 therein, and a supply pump 33 for supplying a predetermined amount of ammonia water at a predetermined temperature. It is provided with. The ammonia water 31 is 900 when the temperature is 20 ° C.
0 μg / liter oxygen is dissolved. It is to be noted that air may be supplied into the tank 32 and bubbling may be performed as necessary to make the oxygen concentration in the tank uniform.

The pH of the discharged water 18 discharged from the autoclave 11 is adjusted to around 7 by a pure water device 22, and oxygen is reduced to zero by a deaeration tank 23. Where water in this state is supplied at a constant flow rate (100 ml / min), ammonia water 3 containing a certain amount of oxygen (9000 μg / liter) at a predetermined temperature (for example, 20 ° C.)
By supplying 1 cc of 1 (dissolved oxygen amount: 9 μg / liter), the pH of water can be set to 9 and a fixed amount of dissolved oxygen (DO = 100 μg / liter) can be obtained.

Thus, the scale can be attached to the pipe material under the same conditions as those of the actual boiler water of the CWT method.

When it is desired to rapidly change the oxygen concentration, the oxygen concentration is increased by increasing the oxygen concentration supplied to the tank 32.

In the above apparatus, by rotating the rotating body 12, a desired flow rate can be obtained even if the supply amount of the supply water 14 is small.
Scale generation at any temperature is possible.

In the present embodiment, the rotating body (diameter: 75 mm) 13 in the autoclave 11 is, for example, about 1000 r.
pm, and the supply water is supplied at a low flow rate (6 liters / H).
４4 m / s). Here, in order to obtain a high flow velocity, the rotation speed of the rotating body 13 may be increased. In the autoclave 11, the supply water 14 can be made uniform by stirring the supply water 14 with a stirring means.

In the present invention, the diameter and the rotation speed of the rotating body 13 are not limited to the above-described ones. For example, as shown in Table 2 and Table 3 below, the rotating body 13 may have various diameters or rotating speeds. Can be varied and the surface speed can be varied to a desired speed.

[Table 1]

[Table 2]

The test piece 12 is cut out from a tube made of a component material applied to an actual machine, and is, for example, a column having a diameter of 10 mm and a height of 6 mm, but is not particularly limited.

Examples of the electrochemical evaluation method of the present invention include a corrosion potential method, an AC impedance method, an ORP (oxidation-reduction potential) method, and the like.

Further, the state of the adhesion of the scale can be confirmed by the laser method. Specifically, among the scale components, Fe ₃ O ₄ (magnetite) and α-Fe ₂
The ratio with O ₃ (hematite) can be measured by laser Raman spectroscopy.

FIG. 4 shows an apparatus capable of measuring the corrosion potential method.
Shown in As shown in FIG. 4, the corrosion evaluation device according to the present embodiment has a platinum electrode 41 provided on the autoclave 11 so as to face the test piece 12 provided on the rotating body 13 in the autoclave 11 shown in FIG. An evaluation device is configured.

Then, the rotating body 13 is stopped, the test piece 12 is opposed to the platinum electrode 41, and an electric current is applied to measure the impedance by the potentiometer 42 (FIG. 5A). reference).

The corrosion potential measured here becomes a state close to that of an insulator when a strong scale 43 adheres to the surface of the test piece 12 (see FIG. 5B), the potential becomes low, and the resistance becomes high. Can be evaluated.

When the scale 43 is not attached or when there is a gap 44 in a part of the scale 43 (see FIG. 5).
(See (a, c)), it can be evaluated that the potential is high and the resistance is low.

Normally, as shown in FIG. 6, the thickness (d) of the scale 43 gradually increases as time (t) elapses.

In the present invention, various evaluations can be made without removing the test piece from the rotating body in the process of attaching the scale. Therefore, it is possible to save the trouble of collecting a sample, and it is possible to measure the potential in an autoclave under the same high-temperature and high-pressure conditions as those of an actual device.

In the AC impedance method, as shown in FIG. 7, a high-temperature pressure-resistant container 51 is provided with a platinum electrode 52 and a counter electrode 53.
And a sample electrode 54 having the test piece 12 and a reference electrode 55 serving as a fixed reference are measured. The counter electrode 53 and the sample electrode 55 have the same configuration, and the periphery of the electrode bar 56 is covered with a high-temperature and high-pressure resistant insulating tube 57 such as Teflon (trade name) or a stainless steel tube 58 to be made high-temperature resistant. The reference electrode 55 is a silver chloride solution 60 interposed on the silver / silver chloride electrode 59 surface.
Are provided inside the insulating tube 61, and the outside thereof is covered with a stainless steel tube 58 so as to be resistant to high temperature and high pressure.

In the above electrode device, the high-temperature pressure-resistant container 51
The state of each layer can be evaluated by supplying the high-pressure and high-temperature supply water 14 under the same conditions as the actual device and measuring the waveform of each layer while changing the frequency from high frequency to low frequency. This makes it possible to determine in which part of the inner layer corrosion is progressing.

The ORP method evaluates how the water environment changes due to a change in the O ₂ concentration in the water.
That is, when the oxygen concentration in the water changes, the value of the ORP changes.

As described above, according to the corrosion evaluation apparatus of the present invention, high temperature (250 to 300 ° C.), high pressure (250 kg / c
m ² ) can be measured. As a result, the scale can be evaluated in a state close to the actual machine.

That is, in the prior art, the potential of the scale attached was measured at normal temperature and normal pressure, so that the behavior of the scale prepared at high temperature and high pressure did not match, and accurate evaluation was impossible. However, according to the present invention, this is solved and the transition of the potential in an actual state can be measured.

According to the present invention, since the measurement can be performed while the scale is generated in the autoclave, the scale is first generated in a normal state, and then the supply water under various conditions is supplied to supply the scale in various states. Can be arbitrarily generated. Therefore, it is possible to evaluate the transition of the scale and the state of destruction assuming various troubles such as a change in O ₂ concentration, a change in pH, a leak of seawater, and the like.

[Second Embodiment] FIG. 3 shows a scale generating apparatus according to the second embodiment. As shown in FIG.
In the autoclave 11 according to the present embodiment, a viewing window 71 is provided in a part of the device main body of the autoclave 11,
This is to make it possible to observe the internal state. Through the viewing window 61, a change with time in the scale generation process on the sample surface can be observed, and evaluation can be performed in an arbitrary state. Further, the scale generation can be continued immediately after the observation.

According to the present invention, as shown in FIG. 9, the water temperature in the pipe near the inlet of the boiler 73 on the downstream side of the high pressure heater 74 for supplying the high pressure water to the boiler 73 for driving the turbine 72 Can evaluate the scale corrosion under the same condition as the high temperature condition of 300 ° C. In addition, 75 is a deaerator, 76 is a heater, and 77 is a condenser.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. Scale generation was performed using an apparatus as shown in FIG. In this embodiment, the rotating body (diameter: 75 mm) 13 is rotated at, for example, about 1000 rpm in the autoclave 11 and the supply water is supplied at a low flow rate (6 L / H), so that the surface of the test piece 12 Flow velocity (4m /
s) could be achieved. As a test piece,
Stainless steel pipe [SB2 (water supply side pipe), STBA24
(Boiler material)], and in this embodiment, the diameter is 10 m.
m and a columnar shape with a height of 6 mm. As a comparison, a supercritical pressure loop test device was used. These temperatures,
The comparison of pressure, flow rate, installation area, and required power is shown in Table 3 below.

[0045]

[Table 3]

As shown in Table 1, the conventional supercritical pressure loop test apparatus required a large amount of water (3 tons / hour), but in this embodiment, a very small supply of 6 liters / hour. I was able to use water. The obtained scale had the same scale properties as the conventional example, and was almost the same.

Thus, according to the present invention, it has been found that the installation area is small, the required power and the required supply water amount can be extremely reduced, and a simple test apparatus can be provided. in this way,
In addition to the downsizing of the device, the required power and the significant reduction of the supply water, the present invention allows the process of scale generation to be observed online. In addition, the potential measurement can be performed in a state where it is installed on the rotating body of the test apparatus, and can be successively provided for different tests, so that various tests can be performed.

[0048]

As described above, according to the invention of claim 1 of the present invention, a rotating body to which a plurality of test pieces are attached in an autoclave, a means for rotating the rotating body, and an autoclave. Since the water supply means for supplying the water is provided, the scale can be generated with a simple device and at a high temperature and a high pressure equivalent to that of an actual machine with a very small amount of supplied water.

According to the second aspect of the present invention, since the viewing port is provided in the autoclave in the first aspect, it is possible to observe a state during the scale generation.

According to the third aspect of the present invention, in the first aspect, a deaeration means for removing oxygen in the supply water to the supply line of the supply water, and a degassing means for supplying a predetermined amount of concentration to the deaerated supply water. And an oxygen supply device for supplying oxygen
The scale generation by the supply water by the T method becomes possible.

According to a fourth aspect of the present invention, there is provided a corrosion evaluation apparatus comprising: the scale generating apparatus according to any one of the first to third aspects; and a platinum electrode provided at a position facing the test piece. Therefore, online electrochemical analysis becomes possible. It is characterized by the following.

According to the fifth aspect of the present invention, since the reference electrode is provided in the fourth aspect, the wake impedance method can be measured, and the properties of the scale can be measured.

According to a sixth aspect of the present invention, there is provided the scale producing method, wherein a rotating body having a plurality of test pieces attached thereto is rotated in an autoclave, and water is supplied into the autoclave.
Since the oxide scale is generated on the surface of the test piece, the scale can be generated with a simple device and at the same high temperature and high pressure as the actual machine even if the amount of supplied water is extremely small.

According to the invention of the method for evaluating corrosion of claim 7, a rotating body having a plurality of test pieces mounted thereon is rotated in an autoclave, water is supplied into the autoclave, and an oxide scale is formed on the surface of the test piece. Generate
Since the electrochemical evaluation is performed in this state, online electrochemical analysis becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a scale generation device according to a first embodiment.

FIG. 2 is a schematic diagram of a scale generation system using the above device.

FIG. 3 is a schematic diagram of an oxygen supply device.

FIG. 4 is a schematic diagram of a corrosion evaluation device according to the present embodiment.

FIG. 5 is a schematic diagram of a corrosion evaluation according to the present embodiment.

FIG. 6 is a diagram showing the relationship between scale generation time and thickness.

FIG. 7 is a schematic diagram of a potential measuring device according to the present embodiment.

FIG. 8 is a schematic diagram of a scale generation device according to a second embodiment.

FIG. 9 is a schematic diagram of a boiler plant.

FIG. 10 is a schematic diagram of conventional scale generation.

FIG. 11 is a schematic diagram of conventional scale generation.

FIG. 12 is a schematic diagram of a conventional scale evaluation.

[Explanation of symbols]

 Reference Signs List 11 autoclave 12 test piece 13 rotating body 14 supply water 15 water supply means 16 stirring shaft of stirring means 17 superheating means 18 discharge water 21 circulation line 22 pure water device 23 deaeration tank 24 high pressure pump 25 oxygen supply device 26 acid conductivity Measuring instrument 27 Electric conductivity measuring instrument 28 Dissolved oxygen measuring instrument 29 pH meter 30 Constant temperature bath 31 Ammonia water 32 Tank 33 Supply pump 41 Platinum electrode 42 Potentiometer 43 Scale 44 Air gap 51 High temperature pressure resistant container 52 Platinum electrode 53 Counter electrode 54 Sample electrode 55 Reference electrode 56 Electrode rod 57 Insulation tube 58 Stainless steel tube 59 Silver / silver chloride electrode 60 Silver chloride solution 61 Insulation tube 71 Viewing window

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G01N 27/30 G01N 27/30 B 33/20 33/20 NF term (reference) 2G050 AA01 BA03 BA10 CA02 CA04 DA01 EA01 EA05 EA06 EB03 EB06 EB07 EC01 EC07 2G055 AA03 BA12 CA07 CA25 DA08 EA06 FA06 2G060 AA10 AE40 AF03 AF06 KA09

Claims (7)

[Claims] 1. A scale generating apparatus comprising: a rotating body to which a plurality of test pieces are attached in an autoclave; means for rotating the rotating body; and water supply means for supplying water to the autoclave. 2. The scale generating device according to claim 1, wherein a viewing window is provided in the autoclave. 3. The degassing means according to claim 1, further comprising: a deaeration means for removing oxygen in the supply water to the supply water supply line; and an oxygen supply device for supplying a predetermined amount of oxygen to the deaeration supply water. A scale generation device, comprising: 4. A corrosion evaluation device comprising: the scale generation device according to claim 1; and a platinum electrode provided at a position facing the test piece. 5. The corrosion evaluation device according to claim 4, wherein a reference electrode is provided. 6. A scale producing method, comprising: rotating a rotating body having a plurality of test pieces mounted therein in an autoclave, supplying water into the autoclave, and producing an oxidized scale on the test piece surface. 7. Rotating a rotating body on which a plurality of test pieces are mounted in an autoclave, supplying water into the autoclave, generating an oxide scale on the test piece surface, and performing an electrochemical evaluation in this state. A corrosion evaluation method characterized by the following.