JPH01123100A - Method and device for defoaming for steel sheet cleaning equipment - Google Patents

Abstract

PURPOSE:To effectively defoam a treating liquid so as to prevent the outflow of the bubbles of the treating liquid generated by cleaning of a steel sheet and to recover the defoamed liquid as the treating liquid by injecting the treating liquid which is of the same kind as said treating liquid and is kept at the temp. lower than said treating liquid to the bubbles of the treating liquid. CONSTITUTION:The steel sheet 2 which is stuck with fats and oils, etc., on the surface is passed in an immersion tank 3, an electrolytic tank 4, etc., and the above-mentioned fats and oils, etc., are cleaned and removed by the air bubbles generated by saponification with an alkaline soln. or electrolysis. The bubbles generated in the treating liquid in the above-mentioned steel sheet cleaning equipment are introduced together with the treating liquid to a spray tank 12 through a sub-tank 7 in which the cleaning and treating liquids such as alkaline liquid are prepd. The treating liquid which is of the same kind as the treating liquid and is kept at the temp. lower than the temp. thereof is injected from spray nozzles 13 provided in the tank to the bubbles. The bubbles are thereby effectively eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a defoaming method and device for a steel plate cleaning facility.

<Prior Art> Conventionally, steel plates have been cleaned using equipment as shown in FIG. That is, as shown in the figure, payoff reel 1
The steel plate 2 unwound from the steel plate coil installed in the is first introduced into an alkali immersion tank 3, then introduced into an electrolytic tank 4, washed with water in a water washing tank 5, and wound up by a tension reel 6. . Here, the immersion tank 3 is filled with an alkaline liquid as a processing liquid, and the alkaline liquid saponifies and washes away fats and oils adhering to the surface of the steel plate 2.

Further, the electrolytic tank 4 is filled with an alkaline solution, and electrodes 4a are installed so as to sandwich the introduced steel plate 2 from both sides. Electricity is applied between the steel plate 2 and the surface of the steel plate 2 to be electrolyzed, thereby generating bubbles and cleaning the surface of the steel plate 2.

The alkaline immersion tank 3 and the electrolysis tank 4 are each provided with a sub-tank 7, and each alkaline solution in the alkali immersion tank 3 and the electrolysis tank 4 is circulated to each sub-tank 7 by a circulation pump 8, and its concentration is adjusted. ,
Temperature adjustments are being made. Further, each sub-tank 7 is provided with an overflow pipe 9 so that excess foam is disposed of into a drainage pit.

<Problems to be Solved by the Invention> In the above-mentioned cleaning equipment, the oil and fat adhering to the surface of the steel plate 2 causes a saponification reaction with the alkali in the treatment liquid, and becomes stone particles in the treatment liquid. Wlunderstand. Therefore, this treatment liquid tends to generate bubbles, so foaming occurs due to stirring of the liquid by passing the steel plate 2 through the liquid, or stirring due to transfer of the liquid by a circulation pump, and the bubbles are generated in the alkali immersion tank 31fiV tank. There is a problem that it flows out from the tank 4 and the sub tank 7.

The outflow of this foam causes a decrease in the amount of alkaline solution used in the cleaning process.
In other words, this results in an increase in the amount of alkaline liquid required for cleaning treatment.
Not only does this increase processing costs, but the spilled foam overflows around the tank and causes operational problems.
It had become an important issue.

SUMMARY OF THE INVENTION In view of these problems, an object of the present invention is to provide a method of preventing bubbles from flowing out in the above-mentioned steel plate cleaning equipment, and an apparatus for realizing the method.

Means for Solving the Problems> A defoaming method in steel plate cleaning equipment according to the present invention that achieves the above object is to saponify a steel plate with oil and fat attached to its surface by introducing it into a treatment solution consisting of an alkaline solution. In steel plate cleaning equipment that cleans oil and fat on the surface of the steel plate using air bubbles generated by electrolysis or electrolysis, a treatment liquid that is the same type as the treatment liquid and has a lower temperature than the treatment liquid is applied to the bubbles generated in the treatment liquid. It is characterized by injecting. In addition, the defoaming device for the steel plate cleaning equipment according to the present invention introduces a steel plate with oil and fat, etc. attached to the surface, into a treatment liquid consisting of an alkaline solution, and removes the oil and fat on the surface of the steel plate by saponification or bubbles generated by electrolysis. In steel plate cleaning equipment for cleaning steel plates, etc., the treatment liquid is bubbled from these tanks by communicating with a treatment tank filled with the treatment liquid or a sub-tank connected to this treatment tank to adjust the concentration, temperature, etc. of the treatment liquid. a spray tank that can be introduced together with the spray tank, and a treatment liquid that is the same type as the treatment liquid and has a lower temperature than the treatment liquid is sprayed onto the foam introduced into the spray tank. It is characterized by comprising a spray nozzle.

In the above-mentioned steel plate cleaning equipment, soap is generated in the processing liquid, and when the processing liquid is stirred, the air mixed in the liquid becomes fine and becomes surrounded by a liquid film, forming bubbles. As shown in FIG. 4, the amount of soap dissolved in the treatment liquid increases as the temperature of the liquid, ie, the temperature of the bubbles, increases. Therefore, the fifth
As shown in the figure, by injecting a low-temperature liquid onto the high-temperature foam a, the temperature of a part of the liquid film of the foam is lowered and the solubility of soap in that part during the night is reduced. Figure 6 (
As shown in a), solid soap d precipitates and aggregates in the liquid film C, and the balance of tension in this part is disrupted, resulting in the destruction of bubbles as shown in Figure 6 (bl). Bubbles maintain a spherical shape, so the surface tension is balanced, but as mentioned above, localized cooling increases the surface tension in that area, impairing liquid fluidity and making it easier to defoam. .

As described above, the present invention does not eliminate foam by the impact when a liquid is injected into the foam.

That is, in the steel plate cleaning equipment described above, even if a liquid having approximately the same temperature as the foam is injected onto the foam, the foam is hardly eliminated.

Practical Examples A preferred apparatus for carrying out the method of the present invention will be described below.

FIG. 1 shows an example in which a defoaming device according to an embodiment is installed in the conventional steel plate processing equipment shown in FIG. 7. Note that the same reference numerals are given to the same and similar parts as in the conventional art, and redundant explanations will be omitted.

As shown in the figure, in this embodiment, the alkali immersion tank 3
A defoaming device 10 is provided, which is connected to each of the sub-tanks 7 attached to the electrolytic tank 4.

The anti-foaming device 10 includes a spray tank 12 connected via a communication pipe 11 so that bubbles generated in the processing liquid in the sub-tank 7 are introduced, and a spray tank 12 disposed at the upper part of the spray tank 12 to introduce the foam generated in the processing liquid in the sub-tank 7. It has a spray nozzle 13 that sprays a liquid that is the same as the treatment liquid and has a lower temperature onto the foam introduced into the spray tank 12. This spray nozzle 13
The liquid is sprayed by a pump 14, and the liquid to be sprayed is supplied from the lower part of the spray tank 12 and cooled by a cooling device (not shown). Note that the treatment liquid in the lower part of the spray tank 12 that does not contain bubbles is returned to the sub-tank 7 via the vibrator 15.

Also, an overflow pipe 16 is provided at the top of the spray tank 12.
are in communication so that excess liquid and foam can be disposed of into a drainage pit.

By providing such a defoaming device 10, the alkaline solution in the alkaline immersion tank 3 and electrolyte 4 can be defoamed by the defoaming device 10 at any time, and its concentration and temperature can be adjusted by the Lζ sub-tank 10. Therefore, no bubbles will flow out, and stable steel plate cleaning processing will be performed.

In addition, it was confirmed in an experiment that 50% or more of the amount of foam was defoamed by defoaming by this defoaming device 10.

Next, an example of a more specific structure of the defoaming device is shown in FIG.

As shown in the figure, the defoaming device [20 is similar to that shown in FIG. The processing liquid in the spray tank 22 is supplied by the pump 24, and the spray header 23b provided with each spray nozzle 23 is provided with a valve 23c, and a pressure gauge 23d. are provided for each. This allows the amount of liquid to be sprayed from each spray nozzle 2311 to be adjusted independently. In addition, in order to return the defoamed treatment liquid to the sub-tank 7, one end of the pipe 25 is connected to the sub-tank 7, and the other end opens near the liquid surface inside the spray tank 22. , the liquid levels in the sub-tank 7 and the spray tank 22 are adjusted. Note that 26 in the figure is an overflow pipe. Further, the pump 24 causes the spray nozzle 2 to
The liquid supplied to 3a is cooled by a cooler 27. Furthermore, a bypass valve 28 is provided to adjust the amount of liquid supplied to the entire spray nozzle 23a.

According to the antifoam bag [20] explained above, the spray tank 2
Depending on the state of the foam introduced into 2, each spray nozzle 2
Since the ejection amount of 3a can be adjusted independently as appropriate, optimal defoaming conditions can be obtained.

In other words, the injection amount and injection pressure from the spray nozzle 23a have an appropriate value of f and depending on the amount of foam and the specific gravity of the foam, and for example, when a large amount of liquid is injected against a small amount of foam, the foam may be increased. Therefore, the injection amount and injection pressure of each spray nozzle 23a are adjusted to avoid these problems and obtain the best defoaming effect.

Further, for example, in the above-described spray tank 22, the spray chamber 22a in the upper part of the tank, in which the spray nozzle 23a is disposed inside, preferably has a structure that is sealed upward.

That is, it is preferable that the tank upper part 22a has a structure that is open only downward, and that the space A is always secured.

With this structure, the space A inside the spray chamber 22a is always filled with air, so that the surface of the foam can be prevented from entering the space A. Therefore, the spray nozzle 23a is not surrounded by bubbles, so that effective spraying can be performed at all times.

FIG. 3 shows an example in which spray chambers are provided in two stages, upper and lower, in the spray tank. As shown in the figure, the spray tank 32, which is connected to the sub-tank through a communication pipe 31, has spray chambers 32a and 32b that are open only downwardly and have a space A inside. A spray nozzle 33a is installed in the air space RA inside these spray chambers 32a and 32b.

33b are arranged respectively, and these spray chambers 3
Bubbles are introduced below 2a and 32b, respectively. In the figure, 35 is a pipe for returning defoamed liquid to the sub-tank, and 36 is an overflow pipe.

According to such a configuration, the spray nozzles 33 m,
Since the spray chambers 33b are arranged in the space A of the spray chambers 32a and 32b, which are always filled with air, the spray chambers 32a and 32b are not enveloped in foam, and defoaming can be performed effectively.

Furthermore, since spraying can be performed in two spray chambers, upper and lower, it is possible to effectively treat even when there is a large amount of foam.

<Effects of the Invention> As explained above, according to the present invention, effective defoaming can be performed, so that the processing liquid that has conventionally been disposed of as foam can be effectively recovered, and the treatment liquid that would otherwise be disposed of as foam can be effectively recovered. Therefore, there is an effect that the processing cost in the cleaning processing equipment is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of a steel plate cleaning equipment equipped with a defoaming device according to one embodiment of the present invention, FIG. 2 is an explanatory diagram showing a defoaming device according to another embodiment, and FIG. FIG. 4 to FIG. 6 are explanatory diagrams showing the principle of the method of the present invention, and FIG. 7 is an explanatory diagram showing a steel plate cleaning equipment according to the prior art. In the drawing, 2 is a steel plate, 3 is an alkali immersion tank, 4 is an electrolysis tank, 7 is a sub-tank, 10.20 is a defoaming device, 12.22.32 is a spray tank] 13, 23 a, 33 a, 33 b 24 is a spray nozzle, 24 is a pump, and 27 is a cooling device.

Claims (1)

[Claims] 1) Cleaning of a steel plate, in which a steel plate with oil and fat, etc. attached to its surface is introduced into a treatment liquid consisting of an alkaline solution, and the oil and fat, etc. on the surface of the steel plate is cleaned by saponification or bubbles generated by electrolysis. A method for defoaming in steel plate cleaning equipment, characterized in that the equipment injects a treatment liquid of the same type as the treatment liquid and at a lower temperature than the treatment liquid to the foam generated in the treatment liquid. 2) In a steel plate cleaning equipment in which a steel plate with oil or fat attached to its surface is introduced into a treatment liquid consisting of an alkaline solution and the oil or fat etc. on the surface of the steel plate is cleaned by saponification or bubbles generated by electrolysis, the above treatment liquid is used. A spray tank that is connected to a processing tank filled with water or a sub-tank that is connected to this processing tank to adjust the concentration, temperature, etc. of the processing liquid and into which the processing liquid can be introduced together with foam; A spray nozzle is provided at the top of the spray tank and sprays a treatment liquid of the same type as the treatment liquid and at a lower temperature than the treatment liquid into the foam introduced into the spray tank. Antifoam device in equipment.