JPS63183197A - Method for recovering salt in molten-salt electroplating device - Google Patents

Abstract

PURPOSE:To enable the recovery and reuse of a deposited salt and to reduce the waste water treating capacity by providing a washing vessel using a solvent not disolving the salt in the rear stage of a plating bath, spraying the solvent onto the surface of a band steel, and separating the salt from the solvent after washing by gravity. CONSTITUTION:A solvent such as benzene and toluene stored in a solvent tank 36, not dissolving the salt, and having the b.p. lower than the temp. of the band steel 22 immediately after plating is sprayed from a nozzle 35 onto the band steel 2 entering the solvent washing vessel 34 from the plating bath 26. The sprayed solvent is vaporized on the surface of the band steel 22, the salt deposited on the surface of the band steel 22 is washed and removed by the expansion of the vapor, and the solvent flows down along with the salt into a separator 37. The vaporized solvent is cooled and condensed, and the condensate is returned to the tank 36. The salt and the solvent are separated by gravity in the separator 37, the salt is returned to the plating bath 26, and the solvent is returned to the tank 36.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a salt recovery method applied to a continuous electrolytic plating apparatus for copper strips using an electrolytic bath of molten salt.

[Conventional technology]

An example of conventional electroplating equipment such as Mu 1 using molten salt is shown in FIG. In the figure, a steel strip 2 unwound from a payoff reel 1 is welded to the end of the preceding steel strip in a welder 5, and then sent to a pretreatment device 5 via a looper 4, where it undergoes degreasing, preheating, etc. Necessary processing is performed before plating. Next, the surface is plated in a plating tank 6, washed in a cleaning tank 7, further dried in a dryer 8, passed through a looper 9 and a shear 10, and then transferred to a tension reel 11.
is wound up.

The plating tank 6 is filled with a plating solution 12, and the surface of the steel strip 2 is plated while passing between electrodes 15 installed in the plating solution.

When the steel strip 2 that has been plated in the plating tank 6 is removed from the plating tank 6, molten salt 12, which is a plating solution, adheres to the surface of the steel strip 2, but this adhered molten salt is washed away with water in a cleaning tank 7. removed. After cleaning, the waste water is sent to a waste water treatment facility (not shown) and treated.

[Problem that the invention seeks to solve]

As mentioned above, the salt adhering to the surface of the copper strip after plating is washed away in the cleaning tank 7, but when the salt used in mulmets etc. is washed with water, it reacts with the water and the plating bath cannot be used again. Therefore, the salt that adheres to the copper strip 2 and is taken out of the plating tank 6 is not consumed as it is, causing a problem of increasing the running cost necessary for manufacturing the plated steel strip. In addition, the amount of salt in the wastewater is large, creating the problem of increasing the scale of wastewater treatment equipment.

In order to deal with such problems, conventional methods have been used to mechanically squeeze out the salt adhering to the steel strip, but this method has limitations and is not a sufficient solution.

The present invention proposes a salt recovery method for a continuous electrolytic plating apparatus that solves these problems.

[Means for solving problems]

The present invention solves the above problem by providing a cleaning tank using a solvent at the latter stage of the plating tank, in which a solvent that does not dissolve salt is sprayed onto the surface of the steel strip. The solution is to separate the solvents based on their specific gravity and reuse them.

That is, the present invention uses a continuous electrolytic plating apparatus that continuously electroplates metal on the surface of a steel strip using molten salt as an electrolytic bath. Molten salt electrolytic plating characterized by cleaning by spraying a solvent that has a low boiling point and is capable of dissolving salt onto the target steel strip surface, and separating the salt from the cleaning solvent based on the difference in specific gravity. This invention relates to a method for recovering salt from an apparatus.

The solvent used in the present invention has a boiling point that is lower than the temperature of the steel strip immediately after plating, so it needs to be liquid when it is ejected from the nozzle, so it must have a boiling point above room temperature. is desirable.

[Effect]

In the method of the present invention, it is important to use a solvent that has a boiling point lower than the temperature of the steel strip immediately after plating and does not dissolve salt. That is, when such a solvent is sprayed onto a steel strip, since the temperature of the copper strip is higher than the boiling point of the solvent, the solvent receives heat from the copper strip and evaporates, becoming a gas. The volumetric expansion caused by the gas and K brings about the effect of mechanically peeling off the salt adhering to the surface of the steel strip, resulting in a cleaning effect.

When plating aluminum with molten salt, for example, when a mixed salt of aluminum chloride, sodium chloride, and potassium chloride is used, the melting point of this salt is 90°C to 110°C, and the plating temperature is 150°C to 25°C.
It is carried out at a normal temperature of 0°C.

In this case, solvents that can be used for cleaning include Freon-115 (boiling point 48°C), perchlorethylene (boiling point 121°C), tetrachlorethylene (boiling point 121°C),
46℃).

When these solvents are sprayed onto the surface of a copper strip at 150° C. to 250° C. immediately after plating, the solvent receives heat from the copper strip and evaporates on the surface of the steel strip, becoming a gas. The salt on the surface of the steel strip is washed away by the volume expansion as it becomes a gas.

The washed salt is mixed into the solvent. In the case of Freon-115, the boiling point is lower than the melting point of the salt, so the mixed salt becomes solid. Therefore, the salt and solvent can be separated by solid-liquid mechanical specific gravity separation (for example, centrifugation). In the case of perchlorethylene, liquid-liquid separation is performed, but a similar method can be used to perform specific gravity difference separation.

In addition, in the present invention, various molten salts are used in addition to the above-mentioned aluminum chloride and sodium chloride, and trichlorethylene, carbon tetrachloride, benzene, toluene, etc. may also be used as cleaning solvents in addition to the above. Can be done.

〔Example〕

An embodiment of the invention is shown in FIG.

In FIG. 1, a steel strip 22 unwound from a payoff reel 21 is welded and connected to the end of the preceding steel strip in a welding machine 25, and then introduced into a pretreatment device 25 via a looper 24, where it is degreased and preheated. Necessary treatments are performed before plating.

After the surface is plated in the plating tank 26, the salt on the surface of the steel strip is washed away with a solvent in the solvent cleaning tank 54. Thereafter, it is washed with water in a washing tank 27, dried in a dryer 2B, passed through a looper 29 and a shear 50, and then wound up on a tension reel 51.

The steel strip 22 that has entered the solvent cleaning tank 54 from the plating tank 26 is
A solvent that does not dissolve the salt stored in the solvent tank 54 is sprayed from the nozzle 55 at room temperature or at a temperature raised to around its boiling point so that it can easily evaporate on the surface of the steel plate. The sprayed solvent evaporates on the surface of the steel strip, and the gas expansion at this time washes away the salt adhering to the surface of the steel strip, and then the salt and the salt are released into Kf! t, and flows into the separator 57.

The solvent that evaporates and becomes a gas is cooled and turned into a liquid, which is then returned to the solvent tank S6. Salt and solvent are separated by specific gravity difference in separator 571C, and the salt is returned to plating tank 26 and the solvent is returned to solvent tank 56.

〔Effect of the invention〕

According to the method of the present invention, it is possible to recover the adhering salts on the surface of the steel strip after plating, which were conventionally washed away and wasted. The processing capacity can be reduced, which has a large economical effect on equipment operation.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the method of the present invention, and FIG. 2 is a diagram showing a conventional technique.

Claims (1)

[Claims] A continuous electrolytic plating device that continuously electroplates metal on the steel strip surface using molten salt as an electrolytic bath removes the salt attached to the surface of the steel strip after plating with a boiling point lower than the temperature of the steel strip immediately after plating. A method for recovering salt from a molten salt electrolytic plating apparatus, characterized in that the surface of the steel strip is cleaned by spraying a solvent that does not dissolve the salt, and the salt is separated from the cleaned solvent based on a difference in specific gravity.