JP2000167591A - Removal of rust/scale or prevention of their adhesion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively and safely remove the rust/scale bonded to the inner surface of a water distributing pipe by performing pulse discharge in the water in a water distributing pipe under a voltage condition of the dielectric breakdown voltage of water or more. SOLUTION: Electrodes 3 (a pair of discharge electrodes) are arranged on the way of a pipe (water distributing pipe 2) and pulse discharge is performed from the electrodes 3 in the water in the water distributing pipe 2 under a voltage condition of the dielectric breakdown voltage of water or more. Shock waves generated by this pulse discharge are utilized, that is, propagated through the water distributing pipe 2 to remove the rust/scale bonded to the inner surface of the water distributing pipe 2 or to prevent this adhesion thereto. Pulse voltage is performed under a voltage condition of the dielectric breakdown voltage of water or more. This voltage condition of the dielectric breakdown voltage of water or more is varied by the kind or amt. of a mineral component such as Ca or Si in water and the amt. of dissolved oxygen in water but desirably set to 40 kV/cm or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the removal or prevention of rust scale adhered to a water pipe by performing a pulse discharge in water in the water pipe.

[0002]

2. Description of the Related Art In a circulating water system in a cooling water system such as a cooling tower, or in a makeup water system such as a boiler, rust generated by scale and dissolved oxygen generated by mineral components such as Ca and Si contained in the water causes clogging of distribution pipes. And various problems such as a decrease in heat exchange efficiency. In order to control and prevent this rust scale, chemical treatment is generally performed. However, continuous injection of the chemical is necessary, so the cost is too high.
There are drawbacks such as the risk of environmental pollution due to drainage. On the other hand, when the rust scale is peeled off by an impact force using a hammer or the like, the water pipe may be damaged, and not all parts of the water pipe can be impacted. Accordingly, there has been a demand for a method for removing rust and scale adhered to a water pipe without using a chemical and without fear of breakage.

[0003]

SUMMARY OF THE INVENTION The present invention is characterized in that the treatment can be performed instantaneously, the cost is low, the rust scale after the treatment is finely pulverized and the water distribution pipe is not blocked, as compared with the prior art. An object of the present invention is to provide a method for removing rust and scale adhered to a water distribution pipe and a method for preventing the adherence, which are environmentally friendly because they have no chemicals.

[0004]

According to the present invention, in order to solve the above-mentioned problems, a rust scale adhered to a water distribution pipe is removed by performing a pulse discharge in water in the water distribution pipe, and adhesion is prevented. . That is, the present invention provides: A method for removing or preventing rust and scale adhering to the water distribution pipe, wherein a pulse discharge is performed in the water in the water distribution pipe under a voltage condition equal to or higher than a breakdown voltage of water,
It is.

Further, in the method of the present invention, preferred embodiments are as follows. 2. 2. The method for removing or preventing rust and scale from adhering to a water pipe according to the above item 1, wherein pulse discharge is performed in water in the water pipe at a voltage condition of 40 kV / cm or more. 3. A method for removing or adhering rust scale according to the above item 1 or 2, wherein an electrode (a pair of discharge electrodes) is provided in the middle of the water distribution pipe, and a shock wave generated by pulse discharge is propagated through the water distribution pipe. . 4. The counter electrode according to claim 1 or 2, wherein a counter electrode (a pair of discharge electrodes) is inserted into the water distribution pipe together with a power cable to make the counter electrode movable in the water distribution pipe and to change a pulse discharge position. How to remove or prevent rust scale. 5. The water distribution pipe is a metal water distribution pipe, the water distribution pipe itself is used as one electrode of a counter electrode (a pair of discharge electrodes), and the other electrode of the counter electrode and a power cable are inserted into the water distribution pipe to directly connect the water distribution pipe. 3. The method for removing or adhering rust scale according to the above item 1 or 2, wherein a pulse discharge is performed to the rust scale, and a position where the pulse discharge is performed can be changed.

Hereinafter, the present invention will be described in detail. An apparatus for removing rust and scale by pulse discharge used in the method of the present invention includes a pulse power supply 1 and a pair of discharge electrodes (electrodes 3) connected to a power supply cable 4 from the pulse power supply 1. It is configured. (See Figures 1-3)

[0007] The pulse discharge in the present invention is performed in the water in the water pipe under a voltage condition equal to or higher than the breakdown voltage of water. The voltage condition higher than the breakdown voltage of water varies depending on the type and amount of mineral components such as Ca and Si contained in the water and the amount of dissolved oxygen contained in the water, but is generally 10 kV / cm or more. , Preferably at least 20 kV / cm, particularly preferably at least 40 kV / cm. The present invention is intended to prevent rust and scale from being removed or prevented from adhering due to the dielectric breakdown of water. It is sufficient that the voltage condition is higher than the dielectric breakdown voltage of water, and it is not necessary to apply a large voltage.
That is, the upper limit of the voltage condition in the pulse discharge is not particularly limited. However, considering the capacity and economic efficiency of the pulse discharge device, the voltage condition of the pulse discharge is preferably 40 to 480 kV / cm, more preferably 40 to 240 kV / cm. Furthermore,
In the present invention, a particularly preferable effect has been confirmed in a pulse discharge using a high-voltage pulse power supply having a voltage of 40 to 480 kV, a pulse time width of 0.1 to 100 μS, and a repetition frequency of about 50 Hz or less. Was.

According to the method of the present invention, the rust scale adhered to the water pipe is removed or prevented by performing a pulse discharge in the water in the water pipe. The principle of the present invention is as follows. are doing. When discharge is performed in water in a water distribution pipe using such a high-voltage pulse power supply, a strong shock wave is generated in the water. This is because high-temperature, high-pressure plasma is instantaneously formed near the discharge path,
Due to rapid evaporation of water molecules. The present invention is intended to remove or prevent the rust scale adhered in the water distribution pipe by transmitting the shock wave generated by the pulse discharge into the water distribution pipe.

[0009]

Next, an embodiment of the present invention (first embodiment)
To the third embodiment) will be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a schematic explanatory view for explaining one embodiment (first embodiment) of a method for removing or preventing rust scale adhered in a water distribution pipe according to the present invention. It is. In the method for removing or preventing rust scale according to the first embodiment, as shown in FIG. 1, an electrode 3 (a pair of discharge electrodes) is installed in the middle of a pipe (water pipe 2), and Pulse discharge is performed from the electrode 3 in water under a voltage condition equal to or higher than the breakdown voltage of water. Utilizing the shock wave generated by this pulse discharge, that is,
By transmitting the shock wave generated by the pulse discharge into the water distribution pipe, the rust scale attached to the water distribution pipe is removed or prevented from adhering.

(Second Embodiment) FIG. 2 is a schematic explanatory view for explaining one embodiment (second embodiment) of a method for removing or preventing rust scale adhered in a water distribution pipe according to the present invention. It is. In the method for removing or preventing rust scale according to the second embodiment, as shown in FIG. 2, instead of fixing a pair of discharge electrodes (electrodes 3) to the water pipe 2, a counter electrode (electrodes 3) is used. Is fixed to a support plate or the like, and inserted into the water distribution pipe 2 together with the power supply cable 4 for supplying power from the pulse power supply 1 so as to be movable in the water distribution pipe 2. This makes it possible to perform pulse discharge at an arbitrary position in the water distribution pipe 2, and to remove or prevent rust scale attached to the water distribution pipe at an arbitrary position in the water distribution pipe 2. .

(Third Embodiment) FIG. 3 is a schematic explanatory view for explaining one embodiment (third embodiment) of a method for removing or preventing rust scale adhered in a water distribution pipe according to the present invention. It is. In the method for removing or preventing rust scale according to the third embodiment, as shown in FIG. 3, when the water distribution pipe 2 is a metal water distribution pipe, the water distribution pipe 2 itself is used as a counter electrode (electrode 3). And the other electrode (electrode 3) of the counter electrode and the power supply cable 4 are inserted into the water distribution pipe 2 to directly perform pulse discharge processing on the water distribution pipe. Also in this case, the pulse discharge processing can be performed at an arbitrary position in the water distribution pipe 2.

[0013]

The present invention will be described below with reference to examples. The samples used in this example are as follows. (Sample) As a sample for the pulse discharge treatment, a scale piece (average vertical length 10 mm × average horizontal length 10 mm × thickness 1 m)
m, which is an irregular-shaped scale piece that is thinly peeled off from a pipe) and a pipe piece with a rust inside (diameter 3)
A 4-split pipe piece obtained by vertically dividing a pipe having a rust inside of 4 mm, a thickness of 3 mm and a length of 25 mm. The chord length with respect to the arc of the four-piece pipe piece was 24 mm). Pipe pieces are non-chemically injected cooling water system iron pipes (that is, iron pipes used in cooling towers without chemical injection treatment), and scale pieces are separated from the inside of another cooling water system pipe. It is. FIG. 4 shows a schematic view of these scale pieces and pipe pieces.

The experimental method in this embodiment is as follows. (Experimental method) The apparatus used in this example was a pulse power source 1,
It comprises an electrode 3 connected thereto and insulated by Teflon (insulator 5), and a metal container 9 to which a counter electrode for receiving the electrode 3 is attached. This schematic diagram is shown in FIG.
Shown in In the rust scale crushing experiment, the treatment vessel (metal vessel 9) was filled with tap water and the pulse voltage was 480 kV.
/ Cm (8kJ / pulse) and 240kV / cm (4kJ / pulse)
Shows an example in which the discharge treatment was performed. In addition, pulse discharge was performed directly using the pipe piece as the counter electrode, and the results were compared with the results of crushing by a shock wave using the counter electrode.

(Results) Removal of Scale Pieces: In an experiment of removing scale pieces, the pulse voltage was 480 kV / cm and the shot was broken in one shot. The distance from the electrode is 25 mm, 50 mm, 75 mm
mm, but they were all crushed.

Rust removal on a pipe piece: In an experiment of removing rust on a pipe piece, with a pulse voltage of 480 kV / cm, the rust on the surface was removed as the number of shots increased, and almost disappeared after 8 shots. (No. of Table 1
1-4). This tendency was the same when the pulse voltage was 240 kV / cm (see Nos. 6 to 8 in Table 1). Therefore, the number of shots is fixed to 2 shots and the pulse voltage is 240 kV / cm
The distance dependence from the electrode was measured. The rust was removed even when the length was 25 mm (see Nos. 7, 9, and 10 in Table 1). This tendency was the same for the pulse voltage of 480 kV / cm and 8 shots (see Nos. 4 and 5 in Table 1). Also,
In the case of direct discharge to the pipe piece, the direct discharge is the power supply voltage of 480 kV
/ Cm, most rust was removed by one shot (see No. 11 in Table 1).

In order to grasp these results quantitatively,
The weight of the rust attached to the pipe piece and the weight of the rust after the discharge treatment were measured to determine the rust removal rate. All rust was removed from the pipe pieces after the discharge treatment with a hydrochloric acid-based cleaning agent, the weight of the pipe pieces having no rust attached (the weight after the inhibitor treatment) was obtained, and the removal rate was obtained by the following equation. The results are shown in Table 1.

A = total weight of rust removed by discharge treatment = (weight before discharge treatment) − (weight after discharge treatment) B = total weight of rust attached to pipe pieces = (Weight before discharge treatment)-(weight after washing with hydrochloric acid)

[0019]

[Table 1]

As a result, the direct discharge in water was 73.
The highest removal rate is 1% (see No. 11). As a result of crushing using a shock wave, the removal rate increases as the number of shots increases, and the increase becomes gentler with the number of shots (see Nos. 1 to 4 and Nos. 6 to 8). Also, the removal rate decreases as the distance of the sample from the center of the electrode increases (see Nos. 7, 9, 10 and Nos. 4, 5). It can be seen that the effect of underwater pulse discharge greatly depends on the number of shots and the distance from the electrode, and that a treatment by direct hit in water is very effective.

In the method of the present invention, the method of removing rust scale adhered mainly to the water distribution pipe has been described in detail.
By the method 3 described above, the rust scale can be prevented from adhering by generating a shock wave in the water distribution pipe by performing pulse discharge constantly or periodically. This method of preventing rust scale adhesion is also included in the method of the present invention.

[0022]

According to the present invention, the pulse discharge processing can be performed instantaneously and at low cost, the rust scale is crushed after the processing, the water distribution pipe is not closed, and no chemical is used. Easy removal of rust and scale and prevention of adhesion.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view for explaining one embodiment (first embodiment) of a method for removing or adhering rust scale adhered in a water distribution pipe according to the present invention, and discharge is performed in the middle of the water distribution pipe 2; This is an example in which an electrode (electrode 3) is provided to perform a pulse discharge process.

FIG. 2 is a schematic explanatory view illustrating one embodiment (second embodiment) of a method for removing or adhering rust scale according to the present invention, in which a discharge electrode (electrode 3) is provided in a water pipe 2; This is an example in which a pulse discharge process is performed while moving. In this embodiment, pulse discharge can be performed at an arbitrary position in the water distribution pipe 2.

FIG. 3 is a schematic explanatory view illustrating one embodiment (third embodiment) of a method for removing or preventing rust scale adhered to a water distribution pipe according to the present invention, wherein the water distribution pipe 2 is made of metal. In some cases, a pulse discharge process is performed using the water distribution pipe 2 itself as one electrode of a counter electrode (electrode 3).
In this embodiment, pulse discharge processing is performed directly on the water pipe, and pulse discharge can be performed at an arbitrary position in the water pipe 2.

FIG. 4 is a schematic view of a scale piece and a pipe piece used in an example of the present invention. The unit of the numerical value in the figure is mm.

FIG. 5 is a schematic diagram of a pulse discharge processing apparatus for removing rust and scale used in an embodiment of the present invention.

[Explanation of Signs] 1: Pulse power supply 2: Water pipe 3: Electrode 4: Power cable connection 5: Insulator 6: Ground 7: Sample piece 8: Tap water 9: Metal container

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Chiaki Igarashi 4-2-1 Motofujisawa, Fujisawa-shi, Kanagawa Inside Ebara Research Institute, Inc. (72) Inventor Hidenori Akiyama 2053- 68

Claims (5)

[Claims] 1. A method for removing or preventing rust and scale from adhering to a water distribution pipe, wherein pulse discharge is performed in water in the water distribution pipe under a voltage condition equal to or higher than a dielectric breakdown voltage of water. 2. The method according to claim 1, wherein the pulse discharge is performed in the water in the water pipe under a voltage condition of 40 kV / cm or more. 3. A method for removing or adhering rust scale according to claim 1, wherein an electrode is provided in the middle of the water distribution pipe, and a shock wave generated by pulse discharge is propagated through the water distribution pipe. . 4. The apparatus according to claim 1, wherein a counter electrode is inserted into the water distribution pipe together with a power cable, the counter electrode is movable in the water distribution pipe, and a pulse discharge position can be changed.
Or the method of removing or adhering rust scale according to 2. 5. The water distribution pipe is a metal water distribution pipe, and the water distribution pipe itself is used as one electrode of a counter electrode, and the other electrode of the counter electrode and a power cable are inserted into the water distribution pipe and directly connected to the water distribution pipe. 3. The method for removing or adhering rust scale according to claim 1, wherein pulse discharge is performed and a position where the pulse discharge is performed is changeable.