JPH11286795A - Defoaming method for steel strip cleaning equipment and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively, surely, rapidly and efficiently execute a defoaming by introducing cavitation air bubbles into a cleaning tank for cleaning steel strip adhering fats and oils on its surface and a circulating tank for circulating and preparing a cleaning liquid and making the air bubbles adsorbed into foams. generated in the respective tanks, thereby braking the foams SOLUTION: The steel strip 1 adhering fats and oils on its surface in a rolling stage is passed through the cleaning tank 2 via a deflector roll 14 and a sink roll 15 and is subjected to degreasing and cleaning with an alkaline cleaning liquid, such as sodium hydroxide. Further, the cleaning liquid is made to flow over form the cleaning tank 2 and is subjected to regulation of the concn., temp., etc., of the cleaning liquid in the circulating tank 4, following which the liquid is circulated via circulation piping 6 to the alkaline cleaning tank 2 by a supply pump 5. Foams 8 are excessively generated by air inclusion at the time of the circulation of the cleaning liquid and the advance of the steel strip 1 in this steel strip cleaning apparatus. The cavitation air bubbles 9 are generated by a generator 10 and are introduced into the cleaning tank 2 and the circulating tank 4. The cavitation air bubbles 9 float in the tanks and are adsorbed onto the foams 8, thereby, the foams are broken and eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a steel strip cleaning equipment,
That is, the present invention relates to a defoaming method and a defoaming device for bubbles generated in an alkaline cleaning tank, an electrolytic cleaning tank, a circulation tank, and the like.

[0002]

2. Description of the Related Art First, FIG. 5 shows a general configuration of a steel strip cleaning facility. The steel strip cleaning equipment includes an alkaline cleaning tank 2, an alkaline scrubber 20, an electrolytic cleaning tank 3,
It comprises a hot water scrubber 21 and a hot water rinsing tank 22. BACKGROUND ART In a cleaning apparatus for a steel strip, in order to remove oils and fats attached to the surface of the steel strip in a rolling process, generally, degreasing cleaning using an alkali cleaning liquid such as sodium hydroxide or sodium orthosilicate is performed.

[0003] The steel strip 1 is washed and removed from the surface of the steel strip 1 by a chemical reaction in an alkali cleaning tank 2 with an alkali cleaning solution, and the surface of the steel strip 1 is brushed and sprayed with an alkali scrubber 20. It is further washed. The next electrolytic cleaning tank 3 is filled with an alkaline cleaning liquid, and the conveyed steel strip 1 is energized by electrodes provided so as to be sandwiched from both sides and electrolytically cleaned.
It is cleaned by a brush in the hot water scrubber 21. Thereafter, the steel strip 1 is finally cleaned by a hot water rinse and transported to the next step. Each cleaning tank is provided with a circulation tank 4, and the concentration and temperature of the cleaning liquid are adjusted in the circulation tank 4.

[0004] By the chemical reaction (saponification) of the oils and fats removed in such a degreasing cleaning step and the alkaline cleaning liquid, a large amount of the alkaline cleaning tank 2, the electrolytic cleaning tank 3 and the circulation tank 4 attached to each cleaning tank are formed. This causes problems that the working environment is remarkably deteriorated due to overflow of the foam outside the tank and the running cost of the cleaning liquid is increased.

To solve these problems, a defoaming method by adding a chemical defoaming agent to a cleaning solution has conventionally been adopted. Further, as shown in FIG. 6, Japanese Patent Application Laid-Open No. 6-49544 discloses that hot air is blown onto the foam surface to eliminate the foam. In FIG. 6, an annealing furnace 1 for annealing a steel strip 1 is shown.
The exhaust gas generated by the exhaust gas 6 is led to a flue 17, and is collected as hot air by an exhaust gas-air heat exchanger 18 in the process, and the alkaline cleaning tank 2 and the electrolytic cleaning tank 3 in which bubbles 8 are generated.
Etc. and the circulation tank 4. 50 ℃ sent
Hot air in the range of 300 ° C. is blown to the foam 8 through a hot air nozzle 19 installed in each tank to perform defoaming.

[0006]

However, in the above-mentioned defoaming method using a chemical defoaming agent, the chemical defoaming agent must be supplied continuously and in large amounts, and the running cost of the expensive chemical defoaming agent increases. There is a problem to do. In addition, Japanese Unexamined Patent Publication No.
In the method disclosed in Japanese Patent No. 49544, a large amount of hot air is required to secure the defoaming ability due to the remarkable bubbling phenomenon accompanying the speeding up of the cleaning equipment for steel strip, and the defoaming is performed reliably and in a short time. However, there are problems such as difficulties in performing such operations and an increase in equipment costs. The present invention has been made to solve such a problem, and has as its object to provide an inexpensive and effective defoaming method and defoaming apparatus.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a cleaning tank for cleaning a steel strip having grease or the like adhered to its surface, and a steel strip cleaning apparatus for eliminating bubbles generated in a circulation tank attached to the cleaning tank. In the defoaming method, cavitation bubbles are introduced or generated in the washing tank and the circulation tank, respectively, and the bubbles in the tank are broken by adsorbing the cavitation bubbles to the bubbles generated in each of the tanks. , Defoam. Further, in addition to the above method, in at least one of the cleaning tank or the circulation tank attached to the cleaning tank, the oil and fat in the cleaning liquid in the tank is removed, and the cleaning liquid after the removal is recirculated and supplied from the upper part of the tank. Eliminate foam generated at the top.

As a specific apparatus for achieving the above-mentioned invention, there is provided a cleaning tank for cleaning a steel strip having grease or the like attached to the surface thereof.
And a defoaming device of a steel strip cleaning facility attached to the cleaning tank and for defoaming bubbles generated in a circulation tank for circulating a cleaning liquid between the cleaning tank and the cleaning tank. A cavitation bubble generator was provided in a circulation pipe or an overflow pipe for circulating the cleaning liquid, and a pipe provided with the cavitation bubble generator was provided in a branched manner so as to introduce cavitation bubbles into the cleaning tank and the circulation tank.

Alternatively, a cavitation bubble generator is provided in the cleaning tank and the circulation tank by applying ultrasonic vibration in the cleaning liquid in the tank or in contact with the outer surface of the tank.
Further, in addition to the above-described apparatus configuration, a circulation pipe for circulating the cleaning liquid in the tank is added to at least one of the cleaning tank and a circulation tank attached to the cleaning tank, and an oil-water separation filter is provided in the pipe.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. (Example 1) As explained with reference to FIG. 5 in the prior art, in the steel strip cleaning equipment, a large amount of bubbles generated by saponification is caused by the alkaline cleaning tank 2 using an alkaline cleaning liquid.
And a cleaning tank such as an electrolytic cleaning tank 3 and a circulation tank 4 provided below these cleaning tanks. FIG. 1 is a system diagram schematically illustrating a defoaming method and a defoaming device in a steel strip cleaning facility. Here, an alkali cleaning tank 2 and a circulation tank 4 attached thereto will be described as an example.

The steel strip 1 is guided into the alkaline cleaning tank 2 via the deflector roll 14, conveyed through the cleaning tank 4 via the sink roll 15, and degreased and washed. A circulation tank 4 is provided below the alkaline cleaning tank 2, and the alkaline cleaning liquid is circulated. The cleaning liquid in the circulation tank 4 is supplied by a supply pump 5,
It is supplied to the alkaline cleaning tank 2 by the circulation pipe 6 and returned to the circulation tank 4 again by the overflow pipe 7. Here, when the cleaning liquid is returned to the circulation tank 4, air is entrained. In the alkaline cleaning tank 2, excessive foaming is caused by air entrainment due to the entry of the steel strip 1.

In this embodiment, a cavitation bubble generator 10 is generated in a circulation pipe 6 for circulating a cleaning solution from a circulation tank 4 to an alkaline cleaning tank 2, and a cavitation bubble 9 is cleaned at a subsequent stage of the cavitation bubble generator. The circulation pipe 6 is branched so as to be introduced into both the tank 2 and the circulation tank 4, and the circulation pipe 6 is connected to both the alkali cleaning tank 2 and the circulation tank 4.

As a result, the cavitation bubbles 9 are first introduced into the alkali cleaning tank 2 and the circulation tank 4 by being introduced, and then the cavitation bubbles 9 float in the tank while repeating compression and expansion. Continuous compression breaking on the washing liquid level. At this time, bubbles 8 generated on the liquid surface
And the bubbles 8 can be broken at the same time. Here, in the cavitation bubble generation device 10, the cavitation bubbles 9 may be generated by applying ultrasonic vibration, or the cavitation bubbles 9 may be generated by centrifugal force generated by forming a swirling flow. Is also good.

Here, the circulation tank 4 is switched to the alkaline cleaning tank 2.
Although the case where the cavitation bubble generation device 10 is provided in the circulation pipe 6 for circulating and supplying the cleaning liquid has been described,
It may be provided in the overflow pipe 7. In that case, the overflow pipe 7 is branched so as to introduce the cavitation bubbles 9 into both the cleaning tank 2 and the circulation tank 4 at a stage subsequent to the cavitation bubble generation device.
The overflow pipe 7 is connected to the alkaline washing tank 2 and the circulation tank 4
Connect to both.

(Embodiment 2) FIG. 2 is a system diagram showing an outline of a defoaming method and a defoaming apparatus in a steel strip cleaning facility according to Embodiment 2. In the present embodiment, the cavitation bubble generator 10 is disposed directly in the alkaline cleaning liquid in the cleaning tank 2, and on the outer bottom surface of the circulation tank 4 in the circulation tank 4. In this case, the cavitation bubble generation device 10 uses the cavitation bubble 9 by applying ultrasonic vibration.
Is generated in the tank.

By the addition of the ultrasonic waves, the alkaline cleaning tank 2
The cavitation bubbles 9 are generated in the inside and the circulation tank 4, respectively, so that the inside of the tank is filled first. Then, the cavitation bubbles 9 float in the tank while repeatedly compressing and expanding, and continuously on the cleaning liquid surface. Compression fracture. At this time, the bubbles 8 can be broken at the same time as they are adsorbed on the bubbles 8 generated on the liquid surface.

Here, the cavitation bubble generator 1
0 in the cleaning tank 2 directly in the alkaline cleaning solution,
Also, in the circulation tank 4, the case where the cavitation bubble generation device by applying ultrasonic vibration is described as an example in which the case where the cavitation bubble is provided on the outer bottom surface of the circulation tank 4 is described.
It may be provided in the cleaning solution of each tank or at the bottom or side of the outer surface of each tank, and the combination thereof is also optional.

(Embodiment 3) FIG. 3 is a system diagram showing an outline of a defoaming method and a defoaming apparatus in a steel strip cleaning equipment according to Embodiment 3. In this embodiment, in addition to the first embodiment, a circulation pipe 13 for circulating the cleaning liquid in the circulation tank 4 is provided.
A circulation pump 12 and an oil-water separation filter 11 are provided in the circulation pipe 13. The oil-water separation filter 11 removes oils and fats after washing the steel strip, thereby suppressing excessive foaming due to a chemical reaction (saponification) between the oils and fats and the alkaline washing liquid. Here, in the oil-water separation filter 11, the rolling oil is separated and removed due to a difference in specific gravity.

In this embodiment, the cleaning liquid from which the fats and oils have been removed is recirculated and supplied from the upper part of the circulation tank 4. Thus, the bubbles 8 accumulated on the cleaning liquid in the circulation tank 4
, The cavitation bubbles 9 can further promote the defoaming action. Here, an example in which the oil and fat in the cleaning liquid is removed in the circulation tank 4 has been described, but the removal may be performed in the alkali cleaning tank 2 instead of in the circulation tank 4. Also, it may be performed in both tanks.

(Embodiment 4) FIG. 4 is a system diagram showing an outline of a defoaming method and a defoaming apparatus in a steel strip cleaning facility showing Embodiment 4. In this embodiment, in addition to the above embodiment 2, a circulation pipe 13 for circulating the cleaning liquid in the circulation tank 4 is provided,
A circulation pump 12 and an oil-water separation filter 11 are provided in the circulation pipe 13. The oil-water separation filter 11 removes oils and fats after washing the steel strip, thereby suppressing excessive foaming due to a chemical reaction (saponification) between the oils and fats and the alkaline washing liquid. Here, in the oil-water separation filter 11, the rolling oil is separated and removed due to a difference in specific gravity.

In this embodiment, the cleaning liquid from which the fats and oils have been removed is recirculated and supplied from the upper part of the circulation tank 4. Thus, the bubbles 8 accumulated on the cleaning liquid in the circulation tank 4
, The cavitation bubbles 9 can further promote the defoaming action. Here, an example is shown in which the oil and fat in the cleaning liquid is removed in the circulation tank 4, but the cleaning may be performed in the alkaline cleaning tank 2 instead of in the circulation tank 4. Also, it may be performed in both tanks. In Examples 1, 2, 3, and 4, an alkaline cleaning tank was used.
Although the circulating tank 4 attached thereto has been described as an example, the steel strip cleaning equipment includes a plurality of cleaning tanks filled with an alkaline cleaning liquid and a circulating tank attached thereto. For example, the electrolytic cleaning tank 3 and the attached circulating tank. The same applies to the case of the circulation tank 4.

[0022]

As described above, according to the present invention, by introducing cavitation bubbles in the steel strip cleaning equipment, it is possible to prevent the working environment from deteriorating and to achieve inexpensive and effective defoaming. In addition, the improvement of the cleaning ability due to the cavitation bubbles can be expected, and the cleaning equipment can be made compact, and thereby, the line speed can be increased. Furthermore, by removing oils and fats that cause a large amount of bubbles to be generated by the oil-water separation filter, the generation of bubbles can be suppressed, and the defoaming effect is further increased in combination with defoaming by cavitation bubbles.

[Brief description of the drawings]

FIG. 1 is a system diagram schematically illustrating a defoaming method and a defoaming device in a steel strip cleaning facility according to a first embodiment of the present invention.

FIG. 2 is a system diagram schematically illustrating a defoaming method and a defoaming device in a steel strip cleaning facility according to a second embodiment of the present invention.

FIG. 3 is a system diagram schematically illustrating a defoaming method and a defoaming apparatus in a steel strip cleaning facility according to a third embodiment of the present invention.

FIG. 4 is a system diagram showing an outline of a defoaming method and a defoaming device in a steel strip cleaning facility according to a fourth embodiment of the present invention.

FIG. 5 is a schematic diagram showing a general configuration of a steel strip cleaning facility.

FIG. 6 is a schematic diagram showing an example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel strip 2 Alkaline washing tank 3 Electrolytic washing tank 4 Circulation tank 5 Supply pump 6 Circulation pipe 7 Overflow pipe 8 Foam 9 Cavitation bubble 10 Cavitation bubble generator 11 Oil-water separation filter 12 Circulation pump 13 Circulation pipe 14 Deflector roll 15 Sink roll 16 Annealing furnace 17 Flue 18 Recuperator 19 Hot air nozzle 20 Alkaline scrubber 21 Hot water scrubber 22 Hot water rinsing tank

Claims (5)

[Claims] 1. A defoaming method for a cleaning tank for cleaning a steel strip having grease or the like attached to a surface thereof, and a steel strip cleaning facility for defoaming bubbles generated in a circulation tank attached to the cleaning tank, In the washing tank and the circulation tank, cavitation bubbles are respectively introduced or generated, and the bubbles in the tank are broken by adsorbing the cavitation bubbles to bubbles generated in each of the tanks.
A defoaming method for steel strip cleaning equipment, which comprises defoaming. 2. In at least one of the cleaning tank and the circulation tank attached to the cleaning tank, oil and fat in the cleaning liquid in the tank is removed, and the removed cleaning liquid is recirculated and supplied from the upper part of the tank to generate the cleaning liquid in the upper part of the tank. The defoaming method of the steel strip cleaning equipment according to claim 1, wherein the defoamed foam is defoamed. 3. A cleaning tank for cleaning a steel strip having grease or the like attached to a surface thereof, and a steel strip attached to the cleaning tank for eliminating bubbles generated in a circulation tank for circulating a cleaning liquid with the cleaning tank. A defoaming device for a cleaning facility, and a cavitation bubble generator provided in a circulation pipe or an overflow pipe for circulating a cleaning liquid between the cleaning tank and the circulation tank,
A defoaming device for a steel strip cleaning facility, wherein a pipe provided with a cavitation bubble generator is branched and disposed so as to introduce cavitation bubbles into a cleaning tank and a circulation tank. 4. A cleaning tank for cleaning a steel strip having grease or the like adhering to the surface, and a steel strip attached to the cleaning tank for eliminating bubbles generated in a circulation tank for circulating a cleaning liquid between the cleaning tank and the cleaning tank. A defoaming device for a cleaning facility, wherein in the cleaning tank and the circulation tank, a cavitation bubble generator is provided by applying ultrasonic vibration in a cleaning liquid in the tank or in a state of being in contact with an outer surface of the tank. Defoaming equipment for steel strip cleaning equipment. 5. A washing tank or a circulation tank attached to the washing tank, wherein at least one of the washing tank and a circulation pipe for circulating a cleaning liquid in the tank is added, and an oil-water separation filter is provided in the pipe. The defoaming device of the steel strip cleaning equipment according to claim 3 or 4.