JP3335006B2 - Cleaning method of metal strip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for degreasing and cleaning oil and foreign matter adhering to a rolled strip of steel or non-ferrous metal.

[0002]

2. Description of the Related Art When a metal strip obtained by rolling is subjected to secondary processing or to be directly commercialized, it is necessary to remove stains such as oils and fats adhered in a rolling step. As a method of cleaning such a metal strip, a method of continuously introducing the metal strip into a cleaning apparatus in which a cleaning chamber and a drying chamber are arranged in series and cleaning and drying the metal strip is performed. . That is, according to this method, the metal strip is immersed in the cleaning liquid in the cleaning chamber, or the cleaning liquid is sprayed from both sides of the metal liquid from the cleaning liquid jet nozzle, thereby removing dirt such as oils and fats attached to the surface. . Further, the cleaned metal strip is subsequently carried into a drying chamber installed in series with the cleaning chamber, and while traveling in the drying chamber, hot air is blown from a hot air jet header onto both sides thereof to adhere thereto. The washing liquid thus dried is dried. As a cleaning liquid used in such a cleaning method, an aqueous solution of a chlorinated solvent such as trichloroethane, perchlorethylene, methylene chloride, an alkali-based detergent or a neutral detergent is used because of its high dissolving power of oils and fats.

[0003]

In the above-mentioned method for cleaning metal strips, the use of the above-mentioned chlorinated organic solvents has been gradually regulated from the viewpoint of protection of the global environment. Wastewater treatment, which occurs in large quantities, has become a problem. So instead of these, naphthenic,
Paraffinic and aromatic hydrocarbon solvents have begun to be used as cleaning liquids. Since the hydrocarbon-based solvent is flammable, it is necessary to avoid the danger of explosion due to discharge ignition when the cleaning chamber is filled with sprays or vapors of the cleaning liquid in order to perform cleaning using the hydrocarbon-based solvent. Therefore, in such a cleaning process, in order to maintain a non-combustible atmosphere in the cleaning chamber,
Usually, measures have been taken to introduce an inert gas into the cleaning chamber to reduce the oxygen concentration below the explosive limit concentration.

[0004] However, when the present inventors retested this method, it was found that hot air flows from a drying chamber adjacent to the cleaning chamber, and the hot air generally uses clean air or the like. It was found that it became difficult to keep the cleaning chamber in a non-combustible atmosphere. In addition, the hot air flowing into the cleaning chamber raises the temperature of the cleaning chamber to increase the evaporation amount of the cleaning liquid, and is further exhausted from the inlet of the cleaning chamber accompanied by the vapor of the cleaning liquid. It was also found that it caused an increase and pollution of the surrounding environment.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to secure safe operation, reduce the loss of the cleaning liquid, and reduce the surrounding environment when cleaning metal strips using a non-volatile and flammable cleaning liquid such as a hydrocarbon solvent. To prevent contamination.

[0006]

Means for Solving the Problems The present inventors have conducted various studies on a method of cleaning a metal strip using a non-volatile and flammable cleaning liquid for the above purpose, and as a result, have found that a method for cleaning a metal strip in a cleaning chamber is described. To achieve the above object by supplying an inert gas, maintaining the pressure in the cleaning chamber and the drying chamber higher than the external pressure, and maintaining the airtightness between the cleaning chamber and the drying chamber as much as possible. And succeeded in proposing the present invention.

That is, according to the present invention, a metal strip is cleaned in a cleaning chamber with a hardly volatile and flammable cleaning liquid (hereinafter, also simply referred to as a cleaning liquid), and then dried in a drying chamber. In the method of cleaning materials, an inert gas is supplied into the cleaning chamber, the pressure in the cleaning chamber and the drying chamber is maintained higher than the external pressure, and the space between the cleaning chamber and the drying chamber is kept as airtight as possible. This is a method for cleaning a metal strip.

As the cleaning liquid used in the present invention, any known cleaning liquid can be used without any limitation as long as it is hardly volatile and flammable. In the method of the present invention, since the pressure in the cleaning chamber and the drying chamber is maintained higher than the external pressure, when the vapor pressure of the cleaning liquid in the cleaning chamber or the drying chamber is high, the vapor of the cleaning liquid leaks out of the apparatus. Accordingly, in order to suppress the leakage of the cleaning liquid vapor out of the apparatus, the degree of volatility of the cleaning liquid is preferably such that the vapor pressure at normal temperature is 50 mmHg or less, and more preferably 10 mmHg or less. Incidentally, the vapor pressure of a hydrocarbon-based solvent, which is a typical cleaning liquid used in the present invention, is several mmHg at room temperature, while the chlorine-based solvent methylene chloride has a vapor pressure of about 340 mmHg at 20 ° C. and trichloroethane has a It is 110 mmHg.

Specific examples of the washing solution suitably used in the present invention include kerosene, decane, undecane,
Dodecane and the like can be mentioned.

[0010] In the cleaning room, the metal strip is cleaned with the cleaning liquid. The cleaning of the metal strip is usually performed by immersing the metal strip in the cleaning liquid or by spraying the cleaning liquid toward the metal strip from nozzles provided above and below the metal strip. Generally, the temperature of the cleaning chamber is preferably room temperature in order to prevent the cleaning liquid from leaking out of the apparatus due to volatilization of the cleaning liquid and losing the cleaning liquid.

The metal strip cleaned in the cleaning room is then sent to a drying room and dried. Drying of metal strip
Usually, it is performed by blowing hot air onto the metal strip.

In the present invention, it is necessary to supply an inert gas to the cleaning chamber and to maintain the pressure in the cleaning chamber and the drying chamber higher than the external pressure. In a cleaning method using a chlorine-based organic solvent, since the cleaning liquid is easily volatile, it has been proposed to maintain a negative pressure in the apparatus with an emphasis on maintaining the machine side environment. If this method is applied to a cleaning method using a flammable cleaning liquid, the cleaning chamber cannot be maintained in a nonflammable atmosphere due to the intrusion of air into the apparatus, which is extremely dangerous in operation. Since the vapor pressure of the cleaning liquid used in the present invention is remarkably low in volatility as compared with that of the chlorine-based organic solvent,
Even if the pressure in the apparatus is slightly higher than the atmospheric pressure, there is no effect on the machine side environment.

[0013] By maintaining the pressure in the washing chamber and the drying chamber slightly higher than the external pressure (pressure outside the apparatus), it is possible to avoid the danger of explosion due to the atmosphere outside the apparatus flowing into the apparatus. . The pressure in each of these chambers is generally 0 m
What is necessary is that it is maintained in the range of 10 mmAq exceeding mAq. Further, if the pressure in the cleaning chamber is higher than the pressure in the drying chamber, it is possible to prevent the atmosphere in the drying chamber from flowing into the cleaning chamber. Therefore, this method is a preferred embodiment in the present invention. In this case, the pressure in the cleaning chamber is 0 m
It is preferable that the pressure in the drying chamber is selected from a range of more than 0 mmAq and 5 mmAq in a range of more than mAq to 10 mmAq.

The method of maintaining the pressure in the cleaning chamber higher than the external pressure is performed by supplying an inert gas to the cleaning chamber. In order to prevent the explosion limit from being reached in the cleaning chamber due to the presence of cleaning liquid vapor, a supply of an inert gas is required. Examples of the inert gas include a nitrogen gas, a helium gas, an argon gas, a neon gas, and the like, and a nitrogen gas is generally used.

As a method for maintaining the pressure in the drying chamber higher than the external pressure, it is preferable to install a hot air blower into the drying chamber and an exhaust blower from the drying chamber, and adjust the blowing air volume and the exhaust air volume. .

The cleaning liquid used in the present invention is hardly volatile, has a high boiling point (about 150 to 200 ° C.), and cannot be easily dried only by the heat energy of hot air. For this reason, usually, the blowing hot air is set to a high speed (50 to 120 m / sec), and the liquid energy on the surface of the metal strip is wiped off by the speed energy of the hot air, and the evaporation speed is increased by making the metal band finer to dry the metal strip. become. In other words, it is necessary to apply a much larger velocity energy to the hot air as compared with the case where a chlorine-based organic solvent is used. This means that the turbulence of the air flow in the drying chamber becomes stronger, and if this influence reaches the cleaning room, not only the non-flammable atmosphere in the room cannot be maintained, but also the loss of the cleaning liquid from the cleaning room increases. become.

In order to prevent this, it is necessary to keep the space between the washing chamber and the drying chamber as airtight as possible. Since a continuous metal strip is running in the washing room and the drying room, it is not possible to maintain a complete airtightness between them. Therefore, in the present invention, it is sufficient that the airtightness between the two chambers can be maintained as much as possible so that the atmosphere in the drying chamber does not flow into the cleaning chamber. For example, a method of providing a buffer chamber between these two chambers and providing a seal roll that sandwiches a metal band running in the buffer chamber from both sides to maintain airtightness can be suitably employed in the present invention. This buffer chamber prevents a part of the hot air blown to the metal strip in the drying chamber from flowing into the cleaning chamber along the surface of the strip, and is caused by a temperature difference between the drying chamber and the cleaning chamber. The influence of the convection airflow on the cleaning room can be prevented.

Hereinafter, a typical flow employed in the cleaning method of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing a typical flow of a cleaning method according to the present invention. Here, a description will be given of a spray cleaning method in which the holding amount of the cleaning liquid is reduced, the danger as equipment for handling dangerous substances is reduced, and the effect of removing adhered foreign substances other than oil is excellent.

The traveling metal strip 1 enters the finish cleaning chamber 3 after removing the oil and foreign matter adhering in the degreasing cleaning chamber 2. A minute amount of oil and extra-fine foreign matter brought in from the degreasing cleaning chamber 2 is washed away in the finishing cleaning chamber 3. The metal strip that has undergone the finish cleaning passes through the buffer chamber 4 and enters the drying chamber 5 where it is dried by hot air. The cleaning tank includes a degreasing tank 16 and a finish cleaning tank 21.
Are arranged in a cascade.
6 and is supplied to the finish washing tank 21 and overflows into the degreasing tank 16. In order to prevent the oil concentration in the degreasing tank 16 from increasing,
A part of the circulating washing liquid is withdrawn and sent to the distillation regeneration device 41. Here, the distillate from which the oil and the removed foreign matter have been removed as sludge is sent to the finish washing tank 21 to dilute a small amount of contaminated liquid brought in from the degreasing washing chamber 2.
It flows into the degreasing tank 16 through the overflow pipe 25.

In the degreasing cleaning chamber 2 and the finishing cleaning chamber 3, spray nozzle groups 6 and 7 are arranged so that both surfaces of the metal strip 1 can be cleaned. When the cleaning liquid is sprayed from these nozzle groups, sprays and vapor of the cleaning liquid are generated in the respective cleaning chambers and mixed with air to form an explosive atmosphere. Therefore, an inert gas is introduced into the cleaning chamber to prevent this. In this case, the nitrogen gas generated by the nitrogen gas generator 39 is sent into the cleaning chambers 2 and 3 through the conduit 38.

After the metal strip 1 has been washed in the non-combustible washing chamber, it enters the drying chamber 5 through the buffer chamber 4. The drying chamber 5 is provided with a blow nozzle group 8 for blowing hot air to both sides of the metal strip 1. The air for blowing is pressurized by an air blower 28 and heated to a predetermined temperature by an air heater 29.
0 is supplied to the blow nozzle group 8. Metal strip 1
The hot air blows the cleaning liquid adhering to the surface of the metal strip with its velocity energy, and evaporates and dries the micronized material by the heat energy. Exhaust blower 3 is used to improve the drying efficiency.
5 quickly exhausts. In such a drying step, the speed energy and the heat energy of the hot air blown affect the drying effect. When using a viscous cleaning liquid that is hardly volatile (having a high boiling point and low vapor pressure), its velocity energy must be significantly higher than when using a chlorine-based solvent, an alkaline-based detergent, or a neutral detergent. Must. As a result, the amount of hot air that has collided with the surface of the metal strip 1 and flows into the cleaning chamber increases, so that the non-combustible atmosphere in the cleaning chamber cannot be maintained, and safe driving cannot be continued.

In order to solve these problems, in the present invention, the drying chamber 5 and the cleaning chambers 2 and 3 are operated with the internal pressure slightly higher than the atmospheric pressure. Further, it is desirable that the pressure in the cleaning chamber be slightly higher than the pressure in the drying chamber. Such pressure equilibrium is performed by adjusting the air blower suction damper 27 and the drying chamber exhaust damper 31 for the drying chamber 5, and the nitrogen generation amount of the nitrogen generator 39 for the cleaning chambers 2 and 3. Achieved by adjustment.

Further, in the present invention, the cleaning chamber and the drying chamber are kept as airtight as possible. As a specific method, a buffer chamber 4 having at least one set of seal rolls 11 is provided between the washing chamber and the drying chamber. Further, in order to improve the blocking effect of the hot air flowing in from the drying chamber 5 by the buffer chamber 4, the partition walls 13 and 14 are provided with baffle plates 1 respectively.
2 is provided on the surface of the seal roll so closely as not to affect the rotation of the seal roll. At the entrance of the metal strip 1 into the buffer chamber 4, a squeezing roll 10 is installed, which also serves to squeeze the adhered liquid in the finishing washing chamber 3 and seal the buffer chamber 4.

The pressure in the cleaning chamber and the pressure in the drying chamber are set to be higher than the atmospheric pressure, and the buffer chamber having the above-described structure is interposed between the cleaning chamber and the drying chamber. The non-combustible atmosphere in the cleaning room is shut off from the air leaking from around the cleaning room, the hot air flowing from the drying room, and the convection due to the temperature difference between the cleaning room and the drying room. Therefore, safe driving can be continued.

The nitrogen gas sent into the cleaning chamber is exhausted from an exhaust pipe 32 at the inlet of the cleaning chamber, and the hot air flowing out of the drying chamber is exhausted from an exhaust pipe 33 at the outlet of the drying chamber by an exhaust blower 35.

[0027]

According to the present invention, the non-flammable atmosphere of the cleaning chamber is maintained, so that the safe cleaning operation can be continued.
Also, by shutting off the hot air flowing from the drying chamber to the cleaning chamber, it is possible to prevent evaporation of excessive cleaning liquid in the cleaning chamber and prevent the cleaning liquid from being taken out of the cleaning chamber excessively. Consumption can be reduced. Further, according to the present invention, since high-speed blowing in the drying chamber is possible, the drying effect is high and the space required for drying can be saved. In addition, if a plurality of buffer chambers are provided, high-speed cleaning of the metal strip can be performed.

[0028]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Using the cleaning apparatus shown in FIG.
The 5 mm copper alloy rolled strip was washed. The washing conditions were as follows.

-Running speed of rolled copper alloy strip: 60 m / min-Cleaning liquid: hydrocarbon solvent (vapor pressure at normal temperature: several mmH)
g) ・ Cleaning liquid temperature: 30 ° C. ・ Spray pressure of the cleaning liquid: 1.0 kg / cm ²・ Spray flow rate: 50 l / min ・ Hot air temperature for drying: 70 ° C. ・ Hot air blowing speed: 80 m / sec ・ Nitrogen gas supply amount: 120 l / min ・ Nitrogen gas concentration: 97% ・ Drying chamber length: 1,000 mm ・ Washing chamber length: 1,500 mm Washing chamber pressure 2 mmAq, drying chamber pressure 1.5 mmAq
, The oxygen concentration in the cleaning chamber became 10% 18 minutes after the start of the supply of nitrogen gas, and the composition of the vapor and oxygen of the cleaning liquid could be removed from the explosion limit. Further, there was almost no leakage of the cleaning liquid outside the cleaning device.

For comparison, the pressure in the cleaning chamber was set to-(2-3) mm.
When Aq and the drying chamber pressure were set to -5 mmAq, the oxygen concentration in the cleaning chamber could not be reduced to 20% or less.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a typical flow of a cleaning method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal strip 2 Degreasing washing room 3 Finish washing room 4 Buffer room 5 Drying room 16 Degreasing tank 21 Finish washing tank 28 Air supply blower 35 Exhaust blower 39 Nitrogen generator

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-B-60-40510 (JP, B2) JP-B-60-40511 (JP, B2) JP-B-58-28353 (JP, B2) Patent 3095592 (JP, B2) B2) Patent 3218264 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B08B 3/00-3/14 C23G 1/00-5/06 B21B 45/02

Claims (1)

(57) [Claims] In a method for cleaning a metal strip in a cleaning chamber, the metal strip is cleaned with a non-volatile and flammable cleaning liquid, and then the metal strip is dried in a drying chamber. A method for cleaning a metal strip, comprising supplying, maintaining the pressure in a cleaning chamber and a drying chamber higher than an external pressure, and maintaining the airtightness between the cleaning chamber and the drying chamber as much as possible.