JP2021137750A - Ultrasonic cleaning device and ultrasonic cleaning method - Google Patents

Abstract

An object of the present invention is to more easily and efficiently clean a steel pipe to be treated whose inner surface has accumulated surface deposits containing contaminants. The present invention is an ultrasonic cleaning device that uses ultrasonic waves to clean a steel pipe to be treated in which surface deposits containing contaminants have accumulated on the inner surface of a base steel pipe, and the device contains a cleaning liquid. a treatment tank in which the steel pipe to be treated is immersed; an ultrasonic application mechanism that applies ultrasonic waves to the cleaning liquid; a dissolved gas control mechanism that controls the amount of dissolved gas in the cleaning liquid; a fine bubble supply mechanism that supplies fine bubbles by using a fine bubble supply mechanism; and a high frequency oscillation material to act. [Selection diagram] Figure 2

Description

The present invention relates to an ultrasonic cleaning device and an ultrasonic cleaning method.

When the soil contains harmful substances (particularly heavy metal pollutants including mercury and arsenic) in the transportation pipes of oil fields, such harmful substances accumulate as deposits in the aged transportation pipes. Therefore, when handling aging transportation pipes, it is necessary to decontaminate harmful substances so that they are below the environmental management standards. In particular, when the harmful substance is a heavy metal pollutant, the adhering substance is taken into the inside of the sedimentary coating, and it is necessary to remove the bottom layer of the deposit to clean it. Therefore, many cleaning steps and costs are required for cleaning. Is required.

One of the cleaning methods used in the purification of soil contamination is a method of eluting and removing pollutants by using an electrochemical method (see, for example, Patent Documents 1 and 2 below). Further, a method of decontaminating a pollutant using a chemical such as an acid or a surfactant has been proposed (see, for example, Patent Document 3 below).

Further, although the types of contamination are different, a method of producing safe waste by peeling the surface coating layer contaminated with radiation with high-pressure water is also being studied (see, for example, Patent Document 4 below). ..

On the other hand, although it is rarely used for decontamination, one of the techniques used for cleaning is ultrasonic cleaning. For example, Patent Document 5 below proposes an apparatus capable of uniformly transmitting ultrasonic waves to a cleaning object even in a large tank. Further, Patent Document 6 below proposes an acid cleaning device that uses a combination of ultrasonic waves having two or more types of frequencies.

Japanese Unexamined Patent Publication No. 2007-21315 International Publication No. 2005/0351449 Japanese Unexamined Patent Publication No. 2004-33812 Japanese Unexamined Patent Publication No. 5-19097 International Publication No. 2018/169050 International Publication No. 2011/067955

However, the electrochemical method as disclosed in Patent Document 1 and Patent Document 2 is a method of removing soil, sludge and deposited substances while circulating between electrodes, and removes contaminants adhering to pipes and the like. It is difficult to remove directly. Further, the method disclosed in Patent Document 3 belongs to the so-called chemical cleaning method, but the chemical cleaning method has a high cost of chemicals and requires a long operation even in the treatment. Further, the method disclosed in Patent Document 4 has little effect on peeling of accumulated matter on the inner surface of a pipe such as a transportation pipe in an oil field, and cannot cope with a large-sized and a plurality of objects to be cleaned.

The method disclosed in Patent Document 5 has a cleaning ability for removing deposits accumulated in pipes (particularly, contaminants contained in the bottom layer of deposits such as heavy metal contaminants). There was room for improvement. Further, in the combination of ultrasonic waves having different frequencies as disclosed in Patent Document 6, in some cases, the ultrasonic waves may interfere with each other and the output balance may be lost. There was room for improvement in terms of efficient use of ultrasonic waves.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to make it easier and more efficient to use a steel pipe to be treated in which surface deposits containing contaminants are deposited on the inner surface. It is an object of the present invention to provide an ultrasonic cleaning apparatus and an ultrasonic cleaning method capable of cleaning.

As a result of diligent studies to solve the above problems, the present inventors have come up with the idea of using a high-frequency oscillator material that generates a high-frequency component of ultrasonic waves by applying ultrasonic waves of a specific frequency. By providing such a high-frequency oscillating material inside the treatment tank, the high-frequency components generated when cleaning the steel pipe to be treated on which surface deposits containing contaminants are deposited on the inner surface of the base steel pipe are separated from the base steel sheet and the surface. It was found that the surface deposits can be removed from the surface of the base steel sheet by acting on the interface with the deposits.
The gist of the present invention completed based on such findings is as follows.

(1) An ultrasonic cleaning device that uses ultrasonic waves to clean the steel pipe to be treated, which has surface deposits containing contaminants deposited on the inner surface of the base steel pipe. A treatment tank in which a steel pipe is immersed, an ultrasonic application mechanism that applies ultrasonic waves to the cleaning liquid, a dissolved gas control mechanism that controls the amount of dissolved gas in the cleaning liquid, and fine bubbles are supplied to the cleaning liquid. A high-frequency oscillating material that is located in the processing tank and is located in the processing tank to act the high-frequency component of the ultrasonic waves on the interface between the base steel pipe and the surface deposits by applying the ultrasonic waves. And, equipped with an ultrasonic cleaning device.
(2) The immersion member, which is located within 1 m from the ultrasonic wave application mechanism and has a hardness HV of 250 to 3000 as defined by JIS Z2242, according to (1). Ultrasonic cleaner.
(3) As the dipping member, granules having an average particle size in the range of 0.1 to 50.0 mm are immersed in the treatment tank with a content of ^{1 × 10 -4 to 10% by volume.} The ultrasonic cleaning device according to (2).
(4) The frequency f of the ultrasonic wave applied from the ultrasonic wave applying mechanism is in the range of 18 to 50 kHz, and the frequency f'is in the range of 50 × f or more and 200 × f or less due to the high frequency oscillating material. The ultrasonic cleaning apparatus according to any one of (1) to (3), wherein a high frequency component is generated.
(5) The frequency f of the ultrasonic waves applied from the ultrasonic wave applying mechanism is in the range of 18 to 50 kHz, and the frequency f'is in the range of 50 × f or more and 200 × f or less with respect to the cleaning liquid. A second ultrasonic application mechanism for applying the second ultrasonic wave is further provided, and the output of the second ultrasonic wave from the second ultrasonic wave application mechanism is 20% of the output of the ultrasonic wave having a frequency f. The ultrasonic cleaning apparatus according to any one of (1) to (4) below.
(6) The ultrasonic cleaning device according to any one of (1) to (5), wherein the cleaning liquid is an alkaline liquid having a pH of 8 to 10.
(7) The ultrasonic cleaning device according to any one of (1) to (6), wherein the cleaning liquid contains sodium sulfide.
(8) The dissolved gas control mechanism controls the amount of dissolved gas in the cleaning liquid so that the amount of dissolved gas is in the range of 1 to 40% with respect to the amount of saturated dissolved gas in the cleaning liquid. The ultrasonic cleaning apparatus according to any one of (7).
(9) The fine bubble supply mechanism supplies fine bubbles having an average bubble diameter in the range of 10 nm to 10 μm so that the bubble density is in ^{the range of 10 4} to ⁹ cells / mL, (1). The ultrasonic cleaning device according to any one of (8).
(10) The method according to any one of (1) to (9), wherein the ultrasonic wave application mechanism applies the ultrasonic waves so that the duty ratio is within the range of 0.2 to 0.8. Ultrasonic cleaning device.
(11) The ultrasonic cleaning according to any one of (1) to (10), wherein the pollutant present in the surface deposit is present within a range of 30 μm from the surface of the base steel pipe. Device.
(12) The pollutant present in the surface deposit is any one of (1) to (11) present in the black oxide film (magnetite layer) located on the inner surface of the base steel pipe. The ultrasonic cleaning device described in 1.
(13) The ultrasonic cleaning apparatus according to any one of (1) to (12), wherein the pollutant is at least one of a mercury-containing compound and an arsenic-containing compound.
(14) This is an ultrasonic cleaning method for cleaning a steel pipe to be treated in which surface deposits containing contaminants are accumulated on the inner surface of the base steel pipe by using ultrasonic waves. The cleaning liquid is contained and the treatment target is described. A treatment tank in which a steel pipe is immersed, an ultrasonic application mechanism that applies ultrasonic waves to the cleaning liquid, a dissolved gas control mechanism that controls the amount of dissolved gas in the cleaning liquid, and fine bubbles are supplied to the cleaning liquid. A high-frequency oscillating material that is located in the processing tank and is located in the processing tank to act the high-frequency component of the ultrasonic waves on the interface between the base steel pipe and the surface deposits by applying the ultrasonic waves. An ultrasonic cleaning method in which the ultrasonic waves are applied to the steel pipe to be processed and the high-frequency oscillating material immersed in the processing tank by using an ultrasonic cleaning device comprising the above.

As described above, according to the present invention, it is possible to more easily and efficiently clean the steel pipe to be treated in which surface deposits containing contaminants are deposited on the inner surface.

It is explanatory drawing for demonstrating the steel pipe to be processed which pays attention in embodiment of this invention. It is explanatory drawing for demonstrating the steel pipe to be processed which pays attention in this embodiment. It is explanatory drawing which showed typically an example of the structure of the ultrasonic cleaning apparatus which concerns on this embodiment. It is explanatory drawing for demonstrating the ultrasonic cleaning apparatus which concerns on this embodiment. It is explanatory drawing for demonstrating the ultrasonic cleaning apparatus which concerns on this embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

(About steel pipes to be processed)
Prior to explaining the ultrasonic cleaning apparatus and the ultrasonic cleaning method according to the embodiment of the present invention, the steel pipe to be processed to be focused on in the embodiment of the present invention will be briefly described with reference to FIGS. 1A and 1B. 1A and 1B are explanatory views for explaining the steel pipe to be processed, which is the focus of the embodiment of the present invention. In the following, for convenience, the coordinate systems shown in FIGS. 1A and 1B will be appropriately used for explanation. In addition to the steel pipe to be treated, valves, flanges, etc. connected to the steel pipe to be treated may also be cleaned together.

The steel pipe to be treated that is of interest in the embodiment of the present invention is used for a transportation pipe or the like in an oil field, and FIG. 1A shows a steel pipe to be treated extending in the y-axis direction in the figure cut along an xz plane. The cross section of the case is schematically shown.

When harmful substances (particularly heavy metal pollutants such as mercury (Hg) -containing compounds and arsenic (As) -containing compounds) are present in the soil of the oil field, as shown schematically in FIG. 1A, the transportation piping of the oil field. Surface deposits containing these pollutants are deposited on the inner surface of the surface, and various deposits are deposited on the surface deposits. The steel pipe to be treated of interest in the embodiment of the present invention is one in which surface deposits containing at least pollutants are deposited on the inner surface of a predetermined base steel pipe as schematically shown in FIG. 1A.

The base steel pipe in the steel pipe to be treated is not particularly limited, and may have any chemical composition as long as it satisfies various characteristics required for the transportation pipe of the oil field. Further, the outer diameter, inner diameter, and wall thickness of the base steel pipe are not particularly limited, and various steel pipes used as transportation pipes in oil fields can be used. The outer diameter of such a base steel pipe is, for example, in the range of 30 to 500 mm, and the inner diameter of the base steel pipe is, for example, in the range of 20 to 460 mm. The wall thickness of the base steel pipe is, for example, in the range of 4 to 20 mm.

Here, in the cross section shown in FIG. 1A, the case where surface deposits and deposits are deposited on the entire inner surface of the base steel pipe is shown, but depending on the cross section, only a part of the inner surface is shown. It can also occur when surface deposits and deposits are deposited, or when surface deposits and deposits are not deposited on all of the inner surface.

FIG. 1B schematically shows a cross section of a steel pipe to be treated, which is of interest in the embodiment of the present invention, when the steel pipe is cut in the axial direction (yz plane in FIG. 1B). In FIG. 1B, the deposits that can be further deposited on the surface deposits are not shown. As a result of studies by the present inventors on the transportation piping of the oil field, pollutants such as Hg-containing compounds and As-containing compounds present in the surface deposits are black oxides located on the inner surface of the base steel pipe. It was revealed that it is often present in the coating (magnetite layer).

As an example, the measurement results of the cleaning pipe 3 samples are shown in Table 1 below. Sample A is a used pipe of natural gas and others, sample B is a used pipe of natural gas, and sample C is a used pipe of crude oil. Each used pipe was cut out as a test piece, and the presence of Hg and As inside the pipe was confirmed by 1) Filter Mode and 2) GeoChem Mode of XRF using DPO-6000-C manufactured by OLYMPUS. In the measurement 1), the surface of the deposit 2 cm × 2 cm is detected, and in the measurement 2), the depth is further measured up to 10 μm. As a result, As was detected in measurement 1), but Hg was hardly detected, and As was not detected in measurement 2), and Hg was detected.

From the analysis results of the Hg-containing compound and the As-containing compound in the surface deposits, as schematically shown in FIG. 1B, the Hg-containing compounds are unevenly distributed on the side close to the surface of the base steel pipe, and the base steel pipe has an uneven distribution. It was clarified that As-containing compounds were unevenly distributed on the side far from the surface. That is, as schematically shown in FIG. 1B, an Hg-containing compound uneven distribution region exists on the side near the surface of the base steel pipe of the surface deposit, and As is contained on the side far from the surface of the base steel pipe. It became clear that the compound uneven distribution region exists.

Further, as a result of further verification, the contaminants in the surface deposits as described above are often present within a range of up to 30 μm from the surface of the base steel pipe (within a range of thickness d = 30 μm in FIG. 1B). It became clear.

When handling aged transportation pipes with surface deposits accumulated on the inner surface as shown in FIGS. 1A and 1B, it is necessary to decontaminate harmful substances so that they are below the environmental management standards. .. In particular, as shown in FIG. 1B, the Hg-containing compound is taken into the inside of the deposit film and needs to be removed down to the bottom layer of the deposit in order to be cleaned. Therefore, many cleaning steps and costs are required for cleaning. Is required.

As a result of diligent studies by the present inventors for the purpose of more easily and efficiently cleaning the steel pipe to be treated in which surface deposits containing contaminants are accumulated on the inner surface as described above, the following The ultrasonic cleaning device and the ultrasonic cleaning method according to the embodiment of the present invention as described in detail in the above have been conceived. Hereinafter, the ultrasonic cleaning apparatus and the ultrasonic cleaning method according to the embodiment of the present invention will be described in detail.

(About ultrasonic cleaning equipment)
Hereinafter, the ultrasonic cleaning device according to the embodiment of the present invention will be described in detail with reference to FIGS. 2 to 4.

FIG. 2 is an explanatory view schematically showing an example of the configuration of the ultrasonic cleaning device 1 according to the present embodiment, and shows a state when the ultrasonic cleaning device 1 is viewed from above the z-axis. The size of each member in the drawing is emphasized as appropriate for ease of explanation, and does not indicate the actual size or the ratio between the members.

As schematically shown in FIG. 2, the ultrasonic cleaning device 1 according to the present embodiment includes a processing tank 10, an ultrasonic application mechanism 20, a dissolved gas control mechanism 30, a fine bubble supply mechanism 40, and a high frequency. It has at least an oscillator 50.

<About processing tank 10>
The treatment tank 10 houses the cleaning liquid 3 used for cleaning the steel pipe S to be treated and the steel pipe S to be treated itself. The type of the cleaning liquid 3 held in the treatment tank 10 is not particularly limited, and a known cleaning liquid such as water can be used, but it is preferable to use an alkaline liquid having a pH of 8 to 10. By using an alkaline solution having a pH of 8 to 10 as the cleaning solution 3, the heavy metal compound is reacted with the alkaline component to change the form into a heavy metal hydroxide, and the high frequency component of ultrasonic waves as described in detail below is obtained. Heavy metals can be removed by generating them more reliably with appropriate strength. Further, known particles or the like may be further added to the cleaning liquid 3 for the purpose of further improving the cleaning property. For example, the cleaning liquid 3 may contain sodium sulfide (sodium sulfide). When the cleaning liquid 3 contains sodium sulfide, the cleaning property of the steel pipe S to be treated as targeted in the present embodiment can be further improved by selective adsorption by the sodium sulfide.

Here, the material used for forming the treatment tank 10 according to the present embodiment is not particularly limited, and may be various metal materials such as iron, steel, stainless steel plate, etc., and fiber reinforced. It may be various plastic resins such as plastic (FRP) and polypropylene (PP), or various bricks such as acid-resistant bricks. That is, as the processing tank 10 constituting the ultrasonic cleaning device 1 according to the present embodiment, it is possible to newly prepare a processing tank made of the above-mentioned material, and existing treatment tanks in various production lines are available. It is also possible to use a treatment tank.

Further, the size of the treatment tank 10 is not particularly limited, but the size of the treatment tank 10 is to be generated more reliably with an appropriate intensity in order to more reliably generate a high frequency component of ultrasonic waves as described in detail below. Is preferably a large processing tank having various shapes such that the liquid level depth is about 0.3 to 2.0 m × the total length is about 4 to 20 m.

<About ultrasonic wave application mechanism 20>
The ultrasonic wave application mechanism 20 applies ultrasonic waves of a predetermined frequency to the cleaning liquid 3, the steel pipe S to be treated, and the high-frequency oscillator 50 housed in the treatment tank 10. The ultrasonic wave application mechanism 20 is not particularly limited, and known ones such as an ultrasonic vibrator connected to an ultrasonic oscillator (not shown) can be used.

Further, in FIGS. 1A to 1D, the case where the ultrasonic wave application mechanism 20 is provided on the wall surface of the processing tank 10 is shown, but the installation position of the ultrasonic wave application mechanism 20 in the processing tank 10 is also particularly limited. Instead, one or a plurality of ultrasonic vibrators may be appropriately installed on the wall surface or the bottom surface of the processing tank 10. If the conditions are such that the ultrasonic waves are uniformly propagated throughout the processing tank 10, the balance of the oscillation load of each ultrasonic vibrator becomes uniform, so that the number of ultrasonic vibrators is a plurality. Even so, interference does not occur between the generated ultrasonic waves. Further, as will be described later, by controlling the amount of dissolved gas in the cleaning liquid 3 held in the treatment layer 10 and supplying fine bubbles to the cleaning liquid 3, the entire treatment tank 10 is more uniformly superposed. It becomes possible to propagate sound waves.

In FIG. 2, 4 + 5 = 9 ultrasonic wave application mechanisms 20 are provided on the wall surface of the processing tank 10 parallel to the y-axis direction, and are provided on the wall surface of the processing tank 10 parallel to the x-axis direction. On the other hand, the case where 2 + 2 = 4 ultrasonic wave application mechanisms 20 are provided is shown. However, the number and installation state of the ultrasonic wave application mechanism 20 are not limited to the example shown in FIG. 2, and may be appropriately set according to the shape and size of the processing tank 10. For example, the ultrasonic wave application mechanism 20 may be installed on only one side of the processing tank 10, or may be installed on both sides as shown in FIG. Further, when it is installed on both sides of the processing tank 10, it may be arranged in a staggered arrangement as shown in FIG. 2, or it may be arranged symmetrically. Further, as shown in FIG. 2, it may be installed on the wall surface of the processing tank 10 parallel to the x-axis direction, or may not be installed on the wall surface of the processing tank 10 parallel to the x-axis direction. Further, the ultrasonic wave application mechanism 20 may be provided only on the inner wall side of the processing tank 10 or may be provided only on the outer wall side.

The frequency f of the ultrasonic waves output from the ultrasonic wave application mechanism 20 is preferably, for example, 18 kHz to 50 kHz. When the frequency of the ultrasonic wave is less than 18 kHz, the ultrasonic wave changes to the audible range and can be propagated into the liquid, but the attenuation becomes large by the propagation in the solid. Furthermore, ultrasonic waves are recognized as noise, which may lead to deterioration of the working environment. In addition, ultrasonic propagation may be hindered by large-sized bubbles generated from the surface of the steel pipe to be treated, and the effect of improving the detergency by ultrasonic waves may be reduced. Further, when the frequency of the ultrasonic wave exceeds 50 kHz, the occurrence of cavitation is reduced, and it may be difficult to remove the deposits. By setting the frequency f of the ultrasonic waves output from the ultrasonic wave application mechanism 20 within the range of 18 kHz to 50 kHz and controlling the amount of dissolved gas and fine bubbles as described in detail below, stronger cavitation is generated. At the same time, it becomes possible to propagate ultrasonic waves over a wider range, and more reliably remove the deposits that are laminated on the surface deposits containing pollutants, and to remove the surface deposits containing pollutants more reliably. It is possible to reliably expose it.

Further, by setting the frequency f of the ultrasonic wave output from the ultrasonic wave application mechanism 20 to 18 kHz to 50 kHz, the high frequency of the ultrasonic wave (frequency f) can be obtained from the high frequency oscillating material 50 described in detail below in a more preferable state. It is possible to generate components. Such high frequency components will be described in detail below.

The frequency f of the ultrasonic wave output from the ultrasonic wave applying mechanism 20 is more preferably 18 kHz to 40 kHz, and further preferably 18 kHz to 35 kHz.

Further, the ultrasonic wave application mechanism 20 according to the present embodiment preferably applies the ultrasonic waves so that the duty ratio is within the range of 0.2 to 0.8. By setting the duty ratio of the ultrasonic wave applying mechanism 20 within the above range, the ultrasonic waves are oscillated in a pulsed manner. Then, when the signal becomes zero, the deposits piled up on the surface deposits fixed by the compressional waves are peeled off and removed from the cracked portion by the ultrasonic cavitation by their own weight. Further, the generation of the high frequency component described in detail below is also pulsed, and it becomes possible to more efficiently remove the surface deposits from the inner surface of the base steel pipe. When the duty ratio is less than 0.2, the ultrasonic irradiation time is too short and sufficient energy is not propagated into the water, so that cavitation does not occur or cavitation that occurs is small, which is preferable. No. On the other hand, when the duty ratio exceeds 0.8, it takes time to peel off the deposits, and it also takes time to remove the surface deposits, which is not preferable. The duty ratio of the ultrasonic application mechanism 20 is more preferably in the range of 0.3 to 0.7, and further preferably in the range of 0.4 to 0.7.

<Dissolved gas control mechanism 30>
The dissolved gas control mechanism 30 controls the amount of dissolved gas in the cleaning liquid 3 held inside the treatment tank 10 within an appropriate range.

In the ultrasonic cleaning apparatus 1 according to the present embodiment, it is preferable to control the amount of dissolved gas in the cleaning liquid 3 to an appropriate value in order to achieve both more uniform ultrasonic propagation and high cleaning performance. The appropriate amount of dissolved gas in such cleaning liquid 3 is preferably in the range of 1% to 40% of the dissolved saturation amount in cleaning liquid 3. When the amount of dissolved gas is less than 1% of the amount of dissolved saturation, cavitation does not occur due to ultrasonic waves, and the ability to improve cleanability (ability to improve surface treatment) by ultrasonic waves cannot be exhibited, which is not preferable. On the other hand, when the amount of the dissolved gas exceeds 40% of the dissolved saturation amount, the dissolved gas hinders the propagation of ultrasonic waves and the uniform propagation of ultrasonic waves to the entire treatment tank 10, which is not preferable. The amount of dissolved gas in the cleaning liquid 3 is preferably 5% to 35% of the dissolved saturation amount in the cleaning liquid 3.

Here, if the temperature of the cleaning liquid 3 changes, the dissolved saturation amount of the cleaning liquid 3 changes. Further, the difference in the molecular momentum (for example, water molecular momentum) of the liquids constituting the cleaning liquid 3 due to the temperature change of the cleaning liquid 3 affects the propagating property. Specifically, when the temperature is low, the molecular momentum of the liquid constituting the cleaning liquid 3 is small, the ultrasonic waves are easily propagated, and the dissolved saturation amount of the cleaning liquid 3 is also high. Therefore, it is preferable to appropriately control the temperature of the cleaning liquid 3 so that a desired dissolved gas amount within the above range can be realized. The temperature of the cleaning liquid 3 depends on the specific treatment content to be carried out using the cleaning liquid 3, but is preferably about 20 ° C. to 85 ° C., for example.

Specifically, the amount of dissolved gas in the cleaning liquid 3 is, for example, preferably 0.1 ppm or more and 11.6 ppm or less, and more preferably 1.0 ppm or more and 10.0 ppm or less. Therefore, the dissolved gas control mechanism 30 adjusts the temperature of the cleaning liquid 3 and the amount of dissolved gas in the cleaning liquid 3 so that the amount of the dissolved gas in the cleaning liquid 3 held in the treatment tank 10 is within the above range. Control.

There are various methods for controlling the amount of dissolved gas, such as vacuum degassing and degassing with chemicals, which can be appropriately selected. Further, the amount of dissolved gas in the cleaning liquid 3 can be measured by a known device such as a diaphragm electrode method and an optical dissolved oxygen meter.

Here, the dissolved gases in the aqueous solution are mainly oxygen, nitrogen, carbon dioxide, helium, and argon, and although they are affected by the temperature and components of the aqueous solution, oxygen and nitrogen occupy most of them.

Note that FIG. 2 shows a case where the dissolved gas control mechanism 30 is installed on a wall surface parallel to the y-axis direction of the treatment tank 10, but the installation position of the dissolved gas control mechanism 30 is shown in FIG. The present invention is not limited to the example, and it can be installed at an arbitrary position in the processing tank 10. Further, the number of dissolved gas control mechanisms 30 is not particularly limited, and may be appropriately set according to the size of the treatment tank 10 and the like.

<About the fine bubble supply mechanism 40>
The fine bubble supply mechanism 40 is a cleaning liquid in which fine bubbles having a bubble diameter (average bubble diameter) corresponding to the frequency of ultrasonic waves applied from the ultrasonic wave application mechanism 20 are held in the processing tank 10 via a supply pipe. It is to supply to the inside of 3. Fine bubbles are fine bubbles having an average bubble diameter of 100 μm or less. Among such fine bubbles, fine bubbles having an average bubble diameter of μm may be referred to as microbubbles, and fine bubbles having an average bubble diameter of nm size may be referred to as nanobubbles or ultrafine bubbles. Fine bubbles improve detergency as the core of ultrasonic cavitation and excite high-frequency components.

When the pressure around the bubble is changed, the bubble vibrates in volume, and the volume vibration has strong non-linearity. While generating sound waves by volumetric vibration and exhibiting non-linear behavior, harmonic components with frequencies n times (n is an integer of 2 times or more) the frequency of the irradiated ultrasonic waves and frequencies 1 / n times. A phenomenon occurs in which a sound wave containing a harmonic component having a harmonic wave is returned (see "Nagare" 24, Journal of the Japanese Society of Fluid Dynamics, Nonlinear Acoustic Characteristics of Microbubbles in an Oscillating Pressure Field, 405-412 (2005)). According to the study of the present inventor, it has been confirmed that cavitation bubbles are generated by ultrasonic irradiation even under conditions that do not contain bubbles, and a high frequency band of weak harmonic components is generated. It was confirmed that when the fine bubble was supplied, the above-mentioned harmonic components were further generated.

However, it has not been confirmed whether it acts on cleaning due to the generation of the high frequency band which is a harmonic component. By supplying fine bubbles, the present inventor improves the detergency as a cavitation nucleus, and the high frequency generated by the non-linear volumetric vibration of the fine bubbles acts on the inner surface of the base steel pipe to improve the detergency. I found out to do.

In the ultrasonic cleaning device 1 according to the present embodiment, the average bubble diameter of the fine bubbles supplied into the cleaning liquid is preferably in the range of 10 nm to 10 μm. Here, the average bubble diameter is the diameter at which the number of samples is maximized in the number distribution related to the diameter of fine bubbles. When the average bubble diameter is less than 10 nm, the fine bubble supply mechanism 40 becomes large, and it may be difficult to supply fine bubbles with the bubble diameter adjusted. Further, when the average cell diameter exceeds 10 μm, it becomes difficult to obtain a harmonic component because the number of volume vibrations due to repeated expansion and contraction until expansion to the resonance diameter is reduced, and further, the air inside the cavitation bubble. Increasing the amount reduces the amount of cavitation that induces abrupt contractions that are effective for cleaning, and ultrasonic energy may not work effectively. Further, if the bubble diameter is too large, the propagation of ultrasonic waves may be hindered by fine bubbles, and the detergency improving effect of ultrasonic waves may be reduced.

The concentration of fine bubbles in the cleaning liquid 3 (density) is preferably 10 ⁴ / ml to 10 ⁹ cells / mL. When the concentration of fine bubbles is less than 10 ⁴ cells / mL are sometimes ultrasonic propagation improving effect by the fine bubbles not sufficiently obtained, also become nuclei of ultrasonic cavitation require less cleaning It is not preferable. Further, when the concentration of fine bubbles exceeds 10 ⁹ cells / mL can be or supposed to apparatus for generating a fine bubble increase the number or large-sized, if the supply of fine bubbles is not realistic Yes, not preferable.

Here, as the basic mechanism for generating fine bubbles, there are various mechanisms such as shearing of bubbles, passage of fine pores of bubbles, cavitation (vaporization) by decompression, pressure dissolution of gas, ultrasonic waves, electrolysis, chemical reaction, etc. However, it can be selected as appropriate. In the fine bubble supply mechanism 40 according to the present embodiment, it is preferable to use a fine bubble generation method capable of easily controlling the bubble diameter and concentration of fine bubbles. Since the amount of dissolved gas may change due to the generation of fine bubbles, it is preferable to generate fine bubbles by cavitation (vaporization) by reducing the pressure to bubble the dissolved gas, in which both the bubble diameter and the concentration can be controlled.

Here, the average bubble diameter and concentration (density) of the fine bubbles can be measured by a known device such as a particle counter in a liquid or a bubble diameter distribution measuring device.

The surface potential of the fine bubbles generated as described above is often negatively charged under the liquid conditions of the general cleaning liquid 3. On the other hand, the object to be cleaned (for example, scale, smut, oil, etc. of the steel pipe) existing on the surface of the steel pipe to be treated is often positively charged, so that fine bubbles reach the vicinity of the object to be cleaned. When it reaches, the fine bubbles will be adsorbed on the object to be cleaned due to the difference in chargeability. Since the ultrasonic cleaning device 1 according to the present embodiment has the fine bubble supply mechanism 40, cavitation is generated by the ultrasonic waves to which the fine bubbles are applied, and the object to be cleaned can be reliably cleaned, and the cleaning object can be cleaned more efficiently. Can be done.

Note that FIG. 2 shows a case where the fine bubble supply mechanism 40 is installed on a wall surface parallel to the y-axis direction of the processing tank 10, but the installation position of the fine bubble supply mechanism 40 is shown in FIG. The present invention is not limited to the example, and it can be installed at an arbitrary position in the processing tank 10. Further, the number of fine bubble supply mechanisms 40 is not particularly limited, and may be appropriately set according to the size of the processing tank 10 and the like.

<About high frequency oscillator 50>
As schematically shown in FIG. 2, the high-frequency oscillator 50 according to the present embodiment is located in the processing tank 10, and the base steel pipe is supplied with fine bubbles by applying ultrasonic waves. A high-frequency component of ultrasonic waves acts on the interface between the surface and the surface deposits. As described above, the present inventor has found that a high high frequency band is generated by providing a high frequency oscillator in combination with the supply of fine bubbles.

Here, FIG. 2 illustrates the case where the four high-frequency oscillators 50 are provided in the processing tank 10, but the installation positions and the number of the high-frequency oscillators 50 are only shown for convenience. The installation position and the number of installations are not particularly limited.

As schematically shown in FIG. 3, when the ultrasonic wave (frequency f) output from the ultrasonic wave applying mechanism 20 is applied to the high frequency oscillating material 50, the ultrasonic waves emitted from the high frequency oscillating material 50 are generated. High frequency components are generated. Further, the high frequency component propagates to the fine bubble to excite a higher high frequency component (frequency f'). The generated high-frequency component enters the base steel pipe from the outside of the steel pipe to be treated, permeates the inside of the base steel pipe, and reaches the interface between the base steel pipe and the region where the Hg-containing compound is unevenly distributed. A high frequency component acts on such an interface to peel off surface deposits from the surface of the base steel pipe. Since the surface deposits are peeled off from the portion of the Hg-containing compound uneven distribution region located on the base steel pipe side, the surface deposits can be efficiently removed from the inner surface of the base steel pipe.

Further, when the surface deposit (more specifically, the region where the Hg-containing compound is unevenly distributed) begins to peel off from the surface of the base steel pipe, the surface deposit becomes cracked. Through these cracks, the ultrasonic waves (frequency f) and fine bubble FB propagating in the cleaning liquid 3 permeate to the vicinity of the surface of the base steel pipe, and the cavitation of the fine bubble FB near the surface of the base steel pipe. Will occur, so that the peeling of surface deposits will proceed further.

The generation position and propagation direction of the high-frequency component are not limited to the example shown in FIG. 3, and are generated at various locations of the high-frequency oscillator 50 depending on the shape and the like of the high-frequency oscillator 50, and further. It propagates to fine bubbles and propagates in various directions.

Here, in order to more reliably generate the high-frequency component as described above with an appropriate intensity, the high-frequency oscillator 50 is preferably located within a range of 1 m from the ultrasonic wave application mechanism 20. That is, the separation distance (distance D in FIG. 3) from the oscillation surface of the ultrasonic wave application mechanism 20 to the surface of the high-frequency oscillator 50 is preferably 1 m or less. It should be noted that the high frequency oscillator 50 existing at a position where the separation distance from the ultrasonic wave application mechanism 20 exceeds 1 m does not mean that the high frequency component is not generated at all, and the generated high frequency component is within the separation distance of 1 m. Although it is relatively weaker than the high-frequency component generated from the existing high-frequency oscillator 50, it contributes to the peeling of surface deposits from the inner surface of the base steel pipe.

Further, in order to more reliably generate the high frequency component as described above with an appropriate strength, the high frequency oscillator 50 is a dipping member having a hardness HV of 250 to 3000 defined by JIS Z2242. preferable. By using the dipping member having the above hardness as the high frequency oscillator 50, the high frequency component can be generated more reliably with an appropriate strength. The hardness HV of the dipping member is more preferably 500 or more and 2000 or less. Examples of the material having the hardness HV as described above include glass (HV550), cemented carbide (HV1700), ceramics (HV2350) and the like. Further, various metal bodies having the hardness HV as described above can function as the high frequency oscillator 50.

Further, as the dipping member as described above, granules having an average particle size in the range of 0.1 to 50.0 mm are 1 × 10 ^{− with respect to the total volume of the cleaning liquid 3 contained in the treatment tank 10.} It is preferable to immerse it in the treatment tank 10 with a content of ^{4 to 10% by volume.} By disposing such granules in the treatment tank 10, the handling of the high-frequency oscillator 50 becomes easier, and in addition, the high-frequency oscillator 50 is reflected and scattered in various places in the treatment tank 10 as described above. It is possible to generate high-frequency components of ultrasonic waves, and the high-frequency components are easily propagated to fine bubbles, so that surface deposits can be removed more efficiently. Regarding the shape of the granular material, it is preferable that there are no pores or pores for absorbing ultrasonic waves, but a shape that reflects and scatters the particles, and more preferably a spherical shape or a spherical hollow body. ..

The average particle size of the granules is more preferably 0.1 to 5.0 mm. The content of the granular material is more preferably 0.1 to 1.0% by volume. The average particle size of the granular material means the particle size at an integrated value of 50% in the particle size distribution obtained by the laser diffraction / scattering method. As the above-mentioned granules, a substance having a particularly high hardness further promotes the generation of high-frequency components.

Further, when the frequency f of the ultrasonic wave applied from the ultrasonic wave applying mechanism 20 is within the range of 18 to 50 kHz, the frequency f'obtained by acting on the fine bubble from the high frequency oscillator 50 as described above. A high frequency component in the range of 50 × f or more and 200 × f or less (that is, f': 900 kHz or more and 10 MHz or less) is generated. The high-frequency component having such a frequency f'has straightness, and more reliably permeates through the base steel pipe and acts on the interface between the base steel pipe and the surface deposits. As a result, the surface deposits are more reliably separated from the inner surface of the base steel pipe.

In addition, in order to further promote the peeling effect of the surface deposits due to the high frequency component as described above, as shown schematically in FIG. 4, an ultrasonic wave having a frequency f in the range of 18 kHz to 50 kHz is applied. In addition to the sound wave application mechanism 20, a second ultrasonic wave application mechanism 25 that applies ultrasonic waves having a frequency f'in the range of 50 × f or more and 200 × f or less may be provided. At this time, the output of the second ultrasonic wave applied from the second ultrasonic wave applying mechanism 25 is relative to the output of the ultrasonic wave having a frequency f (that is, the ultrasonic wave applied from the ultrasonic wave applying mechanism 20). It is preferably 20% or less. If the output of the second ultrasonic wave exceeds 20%, interference with the ultrasonic wave application mechanism 20 for removing deposits may occur, and both may be attenuated, which is not preferable. The output of the second ultrasonic wave applied from the second ultrasonic wave application mechanism 25 is more preferably 10% or less. The installation position and the number of the second ultrasonic wave application mechanisms 25 are not particularly limited as long as they are within the range that satisfies the above-mentioned output conditions.

As described above, the ultrasonic cleaning apparatus according to the present embodiment has been described in detail with reference to FIGS. 2 to 4.

(About ultrasonic cleaning method)
In the ultrasonic cleaning method using the ultrasonic cleaning device 1 according to the present embodiment as described above, the steel pipe to be processed and the high-frequency oscillating material immersed in the processing tank 10 of the ultrasonic cleaning device 1 are subjected to. An ultrasonic wave having a predetermined frequency as described above is applied. As a result, a high-frequency component corresponding to the frequency of the applied ultrasonic wave is generated from the high-frequency oscillator, and this high-frequency component propagates to the fine bubble to excite a higher high-frequency component to form a base steel pipe in the steel pipe to be processed. The generated high-frequency component acts on the interface with the surface deposits. As a result, the surface deposits are peeled off from the position of the interface between the base steel pipe and the surface deposits.

The ultrasonic cleaning method according to the present embodiment has been briefly described above.

Hereinafter, the ultrasonic cleaning apparatus and the ultrasonic cleaning method according to the present invention will be specifically described with reference to Examples and Comparative Examples. The examples shown below are merely examples of the ultrasonic cleaning device and the ultrasonic cleaning method according to the present invention, and the ultrasonic cleaning device and the ultrasonic cleaning method according to the present invention are limited to the examples shown below. It's not something.

(Experimental example)
Using a SUS material having a thickness of 6 mm, a treatment tank having a width of 1 m, a length of 10 m, and a depth of 1 m was formed. A used waste oil pipe having an outer diameter of 100 mm and a length of 2 to 8 m is used as a steel pipe S to be treated, immersed in a treatment tank holding a cleaning liquid for 3 minutes, and the oxide scale remaining in the pipe is washed with water. By doing so, verification was performed. As the cleaning liquid, clean water having a liquid temperature of 30 ° C. was used, and a liquid whose pH was adjusted by electrolysis was used. In addition, separately, a liquid to which sodium sulfide was further added (marked with * in Table 2) was also verified in the same manner.

The ultrasonic oscillator of the ultrasonic application mechanism had an output of 1200 W, and 10 ultrasonic vibrators were fixed on one side of the inner wall of the processing tank at an installation interval of 0.8 m for verification. The frequency of the applied ultrasonic waves was 18 to 80 kHz.

Further, the amount of dissolved gas in the cleaning liquid is controlled so as to be the value shown in Table 2 below with respect to the amount of saturated dissolved gas, and the average cell diameter and number density of fine bubbles are the values shown in Table 2 below. It was controlled to be. Here, as a dissolved gas control mechanism, a film-forming degassing device PDO4000P manufactured by Miura Co., Ltd. was used. For the measurement of the dissolved gas amount, a fluorescent dissolved oxygen meter ProODO manufactured by YSI was used to measure the dissolved oxygen amount (%) with respect to the automatically temperature-corrected air saturation, and used as a value proportional to the dissolved gas amount. Further, as a fine bubble supply mechanism, 2FKV-27M / MX-F13 manufactured by OHR Fluid Laboratory was used. The bubble diameter (average bubble diameter) and concentration of the fine bubbles were measured using the pore electrical resistance method (Multisizer 4 manufactured by Beckman Coulter) and the Brownian motion analysis method (NanoSight nanoparticle analyzer manufactured by Malvern).

Further, with respect to the cleaning liquid, a high-frequency oscillator having a hardness HV specified by JIS Z2242 as shown in Table 2 below is applied at a distance from the ultrasonic application mechanism (more specifically, an ultrasonic vibrator) and. The contents were arranged so as to have the values shown in Table 2 below.

The details of the material having the hardness HV shown in Table 2 are as follows.
HV 550: Soda-lime glass particles (average particle size: 0.1 mm)
HV 660: Borosilicate glass particles (average particle size: 4.0 mm)
HV 187: SUS304 material HV 280: Titanium alloy material HV1800: Ceramic (alumina) balls (average particle size: 40 mm)

Three used waste oil well pipes, which are steel pipes to be treated, were bundled and immersed by a crane while being suspended in the center of the treatment tank, and then the ultrasonic intensity was measured and cleaning evaluation was performed.

The generated high-frequency component was measured by bringing the measuring probe into contact with the immersed tube using the bispectral method of a frequency analyzer (ultrasonic tester NA manufactured by Ultrasonic System Laboratory). For the ultrasonic intensity measurement, an ultrasonic level monitor (19001D manufactured by Kaijo) was used to measure the ultrasonic intensity (mV) of 10 points and 2 rows in the longitudinal direction of the center of the treatment tank. At this time, the relative ultrasonic intensity (measurement result of Comparative Example 1, that is, on the premise that the dissolved gas in the solution is not controlled and the fine bubble is not supplied and the high frequency oscillating material is not provided. Relative intensity when the measured ultrasonic intensity was set to 1) and standard deviation σ were calculated, and the propagation of ultrasonic waves into the steel pipe S to be treated and the inside of the treatment tank was compared.

Further, in this test example, the removal rate of mercury on the tube surface was measured, and the measured removal rate was evaluated as the cleaning performance. More specifically, a part of the tube before and after cleaning was cut out, and the amount of mercury adhered to the surface of the tube was measured by XRF in GeoChem mode using DPO-6000-C manufactured by Olympus, and the amount of mercury adhered in the 2 cm × 2 cm region. Was calculated. The ratio of the amount of mercury removed under each condition to the amount of residual mercury adhering to the surface before cleaning was defined as the mercury deposit removal rate. It is as shown below the evaluation criteria of cleaning performance in Table 2 below.

Removal rate of mercury residual film 100% or less to 95% or more: A
Less than 95% to 90% or more: B
Less than 90% -80% or more: C
Less than 80% -60% or more: D
Less than 60% -40% or more: E
Less than 40%: F

That is, the score A and the score B mean that the cleaning performance was very good, the score C means that the cleaning performance was good, and the score D had some difficulty in the cleaning performance. A score E and a score F mean that the cleaning performance was poor. Scores A to C were accepted.

The setting conditions of the ultrasonic wave application mechanism, the dissolved gas control mechanism, and the fine bubble supply mechanism, and the results obtained by changing the high-frequency oscillator and the cleaning liquid are summarized in Table 2 below.

As is clear from Table 2 above, in the example corresponding to the comparative example of the present invention, the relative ultrasonic intensity may be a relatively small value, the standard deviation becomes large, and the ultrasonic waves are not transmitted uniformly. In addition, the cleanability was also rejected. On the other hand, in the example corresponding to the embodiment of the present invention, the relative ultrasonic intensity became a large value, the standard deviation of the ultrasonic intensity became small, and further, excellent detergency was exhibited.

In the comparison of the used waste oil well pipes used in this test example, other heavy metal compounds were not evaluated, but the mercury-containing compound existing closer to the base steel pipe can be removed by the present invention. In addition, since the deposits could be removed visually, heavy metal compounds incorporated into the deposits without impregnation, especially arsenic-containing compounds, and arsenic-containing compounds and mercury-containing compounds were present. Even if it does, it is presumed that cleaning is possible in the same way.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

1 Ultrasonic cleaning device 3 Cleaning liquid 10 Treatment tank 20 Ultrasonic application mechanism 25 Second ultrasonic application mechanism 30 Dissolved gas control mechanism 40 Fine bubble supply mechanism 50 High-frequency oscillator

Claims (14)

An ultrasonic cleaning device that uses ultrasonic waves to clean the steel pipe to be treated, which has surface deposits containing contaminants deposited on the inner surface of the base steel pipe.
A treatment tank in which the cleaning liquid is stored and the steel pipe to be treated is immersed, and
An ultrasonic wave application mechanism that applies ultrasonic waves to the cleaning liquid, and
A dissolved gas control mechanism that controls the amount of dissolved gas in the cleaning liquid,
A fine bubble supply mechanism that supplies fine bubbles to the cleaning liquid,
A high-frequency oscillator located in the processing tank and applying the ultrasonic waves to act on the interface between the base steel pipe and the surface deposits with a high-frequency component of the ultrasonic waves.
An ultrasonic cleaning device. The ultrasonic wave according to claim 1, wherein the high-frequency oscillator is an immersion member located within 1 m from the ultrasonic wave application mechanism and having a hardness HV of 250 to 3000 as defined by JIS Z2242. Cleaning equipment. Examples immersion member, granules the average particle size is in the range of 0.1~50.0mm is immersed in the processing bath at a content of 1 × ¹⁰ -4 to 10% by volume, according to claim 2 The ultrasonic cleaning device described in. The frequency f of the ultrasonic wave applied from the ultrasonic wave application mechanism is in the range of 18 to 50 kHz.
The ultrasonic cleaning device according to any one of claims 1 to 3, wherein a high-frequency component having a frequency f'in the range of 50 x f or more and 200 x f or less is generated by the high-frequency oscillator material. The frequency f of the ultrasonic wave applied from the ultrasonic wave application mechanism is in the range of 18 to 50 kHz.
A second ultrasonic wave application mechanism for applying a second ultrasonic wave having a frequency f'in the range of 50 × f or more and 200 × f or less to the cleaning liquid is further provided.
The ultrasonic wave according to any one of claims 1 to 4, wherein the output of the second ultrasonic wave from the second ultrasonic wave application mechanism is 20% or less with respect to the output of the ultrasonic wave having a frequency f. Cleaning equipment. The ultrasonic cleaning device according to any one of claims 1 to 5, wherein the cleaning liquid is an alkaline liquid having a pH of 8 to 10. The ultrasonic cleaning device according to any one of claims 1 to 6, wherein the cleaning liquid contains sodium sulfide. Any of claims 1 to 7, wherein the dissolved gas control mechanism controls the amount of dissolved gas in the cleaning liquid so that the amount of dissolved gas is in the range of 1 to 40% with respect to the amount of saturated dissolved gas in the cleaning liquid. The ultrasonic cleaning apparatus according to item 1. The fine bubble supply mechanism, the fine bubbles is within the average cell diameter of 10 nm to 10 [mu] m, supplied as cell density is in the range of ¹⁰ 4 to 10 ⁹ / mL, of claims 1 to 8 The ultrasonic cleaning device according to any one item. The ultrasonic cleaning device according to any one of claims 1 to 9, wherein the ultrasonic wave applying mechanism applies the ultrasonic waves so that the duty ratio is within the range of 0.2 to 0.8. The ultrasonic cleaning device according to any one of claims 1 to 10, wherein the pollutant present in the surface deposit is present within a range of 30 μm from the surface of the base steel pipe. The ultrasonic according to any one of claims 1 to 11, wherein the pollutant present in the surface deposit is present in a black oxide film (magnetite layer) located on the inner surface of the base steel pipe. Ultrasonic cleaner. The ultrasonic cleaning device according to any one of claims 1 to 12, wherein the pollutant is at least one of a mercury-containing compound and an arsenic-containing compound. This is an ultrasonic cleaning method that uses ultrasonic waves to clean the steel pipe to be treated in which surface deposits containing contaminants are deposited on the inner surface of the base steel pipe.
A treatment tank in which the cleaning liquid is housed and in which the steel pipe to be treated is immersed, an ultrasonic application mechanism for applying ultrasonic waves to the cleaning liquid, and a dissolved gas control mechanism for controlling the amount of dissolved gas in the cleaning liquid. , A fine bubble supply mechanism that supplies fine bubbles to the cleaning liquid, and the ultrasonic waves that are located in the processing tank to apply the ultrasonic waves to the interface between the base steel pipe and the surface deposits. Using an ultrasonic cleaning device equipped with a high-frequency oscillating material that acts on the high-frequency component of sound waves,
An ultrasonic cleaning method in which the ultrasonic waves are applied to the steel pipe to be processed and the high-frequency oscillator material immersed in the processing tank.

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