JPS63183198A - Method for recovering gaseous salt in molten-salt electroplating device - Google Patents

Abstract

PURPOSE:To directly recover the gaseous salt in exhaust gas and to dispense with the waste water treatment for treating the gaseous salt cooling the exhaust gas from the inside of a plating bath to form the fumes or mist which are collected by a succeeding collector. CONSTITUTION:The vapor of the molten salt exists in the space in the plating bath 26, and the bath is evacuated and kept and a negative pressured to prevent the leakage of the outside. The exhaust gas contg. the gaseous salt is indirectly cooled in a cooler 33, hence only the gaseous salt having a low vapor pressure remains in the exhaust gas, and the excess salt is condensed into fumes of mist and suspended in the exhaust gas. The salt in the form of fumes or mist is collected in the collector 34, and then the exhaust gas is discharged by an exhaust fan 35.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a gas ring 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 Aj using molten salt is shown in FIG. In the figure, a steel strip 2 rewound from a payoff reel 1 is welded to the end of the preceding steel strip by a welder 5, and then sent to a pretreatment device 5 via a louver 4, where it undergoes degreasing, preheating, etc. Necessary processing is performed before plating. Then, after the surface is plated in the plating tank 6,
It is washed and dried in the post-processing device 7, passed through a looper 8 and a shear 9, and then wound onto a tension reel 10.

The plating tank 6 is filled with a molten salt plating solution 11, and the surface of the steel strip 2 is plated while passing between electrodes 12 installed in the plating solution.

Molten salt vapor exists in the space inside the plating tank 6. Since this steam is harmful to the human body if it leaks to the outside of the plating tank 6, it is exhausted into the plating tank 6 and maintained at a negative pressure with respect to the outside.

The exhaust gas from the plating tank 6 is exhausted by an exhaust fan 14 after gaseous salts in the exhaust gas are removed by an absorption cleaner 15.

[Problem that the invention seeks to solve]

As mentioned above, the exhaust from the plating tank 6 is transferred to the absorption cleaner 1
In step 5, gaseous salts in the exhaust gas are removed by spraying water or the like. In this treatment, if the gaseous salt reacts with water, it is possible to recover the salt by drying the treated solution, but if it reacts with water, the salt cannot be recovered.

Therefore, when salt reacts with water, the salt carried out by the exhaust gas becomes a loss due to consumption. This poses a problem of increasing the running cost required for manufacturing the plated steel strip.

Furthermore, an increase in the amount of salt in wastewater causes a problem in that the scale of wastewater treatment equipment and treatment costs increase.

Although it is possible to use a solvent instead of water, it is not a sufficient solution since it requires further post-treatment.

The present invention proposes a gaseous salt recovery method for a continuous electrolytic plating apparatus that solves this problem.

[Means for solving problems]

The present invention solves the above problem by cooling the exhaust gas from the plating bath with a cooler, converting the gaseous salt in the exhaust gas from gas to fume or mist, and then collecting the gas with a filter or an electrostatic precipitator installed. This problem can be solved by collecting and collecting dust using a dust device.

That is, the present invention uses a cooler to cool the exhaust gas from the plating tank in a continuous electrolytic plating apparatus that continuously electroplates metal on the surface of a steel strip using molten salt as an electrolytic bath, and to generate mist from the gaseous salt in the exhaust gas. Alternatively, the present invention relates to a gaseous salt recovery method for a molten salt electrolytic plating apparatus, which is characterized in that fumes are collected and recovered by a dust collector.

[Effect]

In the present invention, the exhaust gas containing gaseous salts is first indirectly cooled by a cooler. Here, the gaseous salts in the exhaust gas can exist in gaseous form only at low vapor pressures, and excess salts coagulate with each other and become suspended in the exhaust gas as fumes or mist.

These flames or mist can be collected by various types of dust collectors, such as filters or electric dust collectors, depending on their particle size.

Therefore, salt can be directly recovered by the method of the present invention, in which the exhaust gas is cooled to form a fume or mist, which is then collected by a dust collector.

〔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 by a welding machine 2S, and then sent to a pretreatment device 25 via a looper 24, where it is degreased and preheated. Necessary treatments are performed before plating. Next, the surface is plated in a plating tank 26, washed and dried in a post-processing device 27, passed through a looper 28 and a shear 29, and then wound up on a tension reel 50.

The plating tank 26 is filled with a plating solution 31 of molten salt,
The surface of the steel strip 22 is plated while passing between electrodes 32 placed in a plating solution. Although molten salt vapor exists in the space within the plating tank 26, it is evacuated and maintained at negative pressure to prevent leakage to the outside.

The exhaust gas from the plating tank 26 is cooled by a cooler 55, and the generated 7 yum or salt in the form of mist is collected and recovered by a dust collector 54, and then exhausted by an exhaust fan 55.

As a specific example, aluminum plating using a mixed molten salt of aluminum chloride and sodium chloride will be described.

The vapor pressure of aluminum chloride is α01, Hg at 20°C, and 50 @Hg at 150°C. Since the inside of the plating tank is operated at a temperature of 150° C. or higher, 50 mag or more of aluminum chloride vapor is present in the gas inside the tank.

When the exhaust gas containing this vapor is cooled to about 20° C. in a cooler, the vapor becomes almost fume. This fume has a particle size of a few microns and can be collected and recovered using a filter or electrostatic precipitator.

[Effects of the Invention] According to the method of the present invention, gaseous salts in the exhaust can be recovered from the plating tank, which was conventionally discharged and consumed, and running fumes during the production of plated steel strips can be reduced. Further, wastewater treatment for gaseous salt treatment can be omitted, which has a large economical effect on equipment operation.

Brief description of the front surface 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] In a continuous electrolytic plating device that continuously electroplates metal on the surface of a steel strip using molten salt as an electrolytic bath, the exhaust from the plating tank is cooled by a cooler, and the mist or fume generated from the gaseous salt in the exhaust is collected by a dust collector. A gaseous salt recovery method for a molten salt electrolytic plating device, which is characterized by collecting and recovering gaseous salt using a molten salt electrolytic plating device.