JPH09143655A - Dross removing device for galvanizing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently separate and recover zinc and dross by providing a device for removing the dross from dross-contg. molten zinc with an attachable and detachable carbon filter, heating means and an automatic scraping means. SOLUTION: The carbon filter 8 is mounted with a prescribed angle at the housing of the dross removing device 1 and the inside of the device housing is previously heated up by the gas burner heating means 2 and the heater heating means 3. The angle of the carbon filter 8 is adjusted by an actuator for an inclining means and the dross 16 contg. the zinc is supplied onto the carbon filter 8 from a feeding port 19, by which the zinc is separated and filtered from the dross 16. The filtered zinc 17 is recovered into a receiving bag 6. If, on the other hand, the residual dross 18 remains on the filter 8, the residual dross 18 is heated to a sherbet form by the gas burner heating means 2. The scraping actuator 4 is actuated to be descended ant the residual dross 18 is discharged from a discharge port 14 by a scraping plate 9 and is recovered into a receiving bag 7.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a dross removing device in hot dip galvanizing.

[0002]

2. Description of the Related Art As steel sheets for automobiles, especially for North American export vehicles, rock salt is sprayed to prevent freezing in winter, so that plated steel sheets for vehicle bodies are required to have higher corrosion resistance. It suffices that zinc is coated to a set thickness, but in the plating process, plating scratches will occur if more than the set plating thickness (for example, 30 μ) is mixed in.
Product value is reduced in appearance. Also, the dross taken in electrochemically becomes a binary compound of Fe.Al.Zn or a ternary compound to generate a secondary current and cause corrosion.

Dross includes top dross floating on the surface of the zinc bath, floating dross floating in the liquid, and bottom dross settling on the bottom. Of these, the top dross is Fe ₂ Al that reacts with solid fine particles formed by the reaction of the steel plate and zinc, or with Al and the like contained in the liquid.
What floats on the liquid surface as a ternary compound of ₅ or Fe / Al / Zn, or finely divided zinc separated from the gas squeezing device, reacts with oxygen in the air to become zinc oxide, which also floats. I will indicate what I did. Also, bottom dross means Fe
Fine particles composed of Zn _{7 and the} like gradually grow and have a specific gravity slightly higher than that of molten zinc, so that they are deposited on the bottom of the apparatus.

[0004] At present, when a certain amount of dross is accumulated in the field, the dross is usually pumped up with a long ladle made of stainless steel wire mesh, drained and transferred to a container called dross bag for disposal. This stainless steel wire mesh has a very low filtration efficiency (efficiency of not discarding pure zinc as much as possible). That is, if the mesh of the wire mesh is made coarse in order to shorten the draining time, large dross will be collected in the zinc tank, and if it is made small, the filtration time will be too long. Moreover, there is a drawback that a large amount of pure zinc has to be discarded together with the dross due to clogging.

In particular, the continuous hot-dip galvanizing line in recent years has been increased in line speed from 180 m / min to 200 m / min, and the amount of top dross generated along with it is about 90.
It is kg / hr. Therefore, a method for recovering zinc contained in top dross has been conventionally developed. For example, Japanese Patent Publication No. 58-026418 discloses a method of recovering zinc by providing a double saucer, providing a small hole in the upper saucer, providing a vibrator facility at the lower part of the saucer, and applying vibration. Japanese Patent Publication No. 59-052939 discloses a method of removing ZnO from a floating dross and then recovering zinc from the floating dross by using a ceramics filter.

Further, Japanese Patent Laid-Open No. 63-140070 discloses a method of using a ceramics filter in a box of a removing device and sending molten zinc into the box by a pump to recover minute impurities by head pressure difference or the like. However, the vibrating method using the double tray has a problem that the dross passes through the small holes of the tray and the top dross before the collection is solidified. The method using the ceramics filter has a problem that the clogging of the filter is severe and the ceramics filter is disposable, so that the cost of removing the dross is high and that the dross accumulated on the filter cannot be recovered after separation. .

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the problems introduced in each of the above-mentioned inventions, and efficiently contains zinc contained in various dross such as top dross generated in a plating bath during hot dip galvanization. It is an object of the present invention to provide an apparatus for improving the basic unit of plated metal by separating and collecting.

[0008]

In view of the above object, the present inventor has completed the device of the present invention as a result of earnest research, and is characterized by removing dross from molten zinc containing dross. The device has a detachable carbon filter, heating means, and automatic scraping means.

The apparatus of the present invention is provided with an inlet for molten zinc containing dross at the upper portion and an outlet for molten zinc with a filter attached at the lower portion.

The filter for separating the dross used in the present invention is a carbon filter. The carbon filter mentioned here has a turbostratic structure in which crystals of carbon are extremely small, is characterized by high hardness and gas impermeability, and is composed of a so-called glassy, non-oriented microstructure. The fracture surface is also black glass, which is different from the granular structure like general carbon materials. Starting materials for carbon are phenol resin, furan resin, carbodiimide, cellulose, etc., which are gradually carbonized. The porous material used in the present invention is a material having the above-mentioned starting material and a low melting point,
For example, particles of acrylic, urethane, NBR, etc. are dispersed and maintained at a temperature intermediate between the melting points of the two, and the low melting point material is melted and permeated into the solid to form a porous body. It is obtained by firing and carbonizing this. It is made of glassy carbon and has a melting point of 37.
It is resistant to heat at about 00 ° C, and has a poor affinity with dross as compared with a ceramic filter, so that dross does not enter the filter and clogging does not occur. For this filter, it was good to select a mesh of 3.5 to 5.0 mm in the experiment.

The heating means may be any means such as a burner heating means, an electric heater heating means and the like. This is for maintaining the inside of the apparatus at a high temperature. Naturally, since the zinc solidifies below the melting point of the molten zinc, it is necessary to maintain the temperature above that. Furthermore, in order to improve the filtration efficiency, it is desirable to raise the temperature during filtration. For example, it is about 700 to 800 ° C.

As the heating means, both burner heating means and electric heater heating means are provided. When zinc is not introduced, heating is performed by the burner heating means in the apparatus, and when zinc is introduced, switching to the electric heater heating means is also preferable. Is. This is to prevent the quality deterioration of molten zinc due to the exhaust gas from the burner heating means. In addition, if all of them are electric heater heating means, running cost will be increased and the temperature rising rate will be slow. Therefore, the switching method is preferable.

The burner heating means is of a direct type in which a flame is present in the apparatus, and its combustion exhaust gas is discharged from the molten zinc introduction port. In the case of a continuous type or a closed type in which the device is hermetically sealed, a duct having a separate valve may be provided and the duct may be discharged from there.

The electric heater heating means may be an ordinary one, but it is desirable to provide it on the wall surface of the entire apparatus for efficient heating.

The automatic scraping means is driven by a driving device such as a motor or a pneumatic actuator and removes dross from the filter. Usually, a plate-shaped object (scraping tool) is used for pressure removal. Of course, the scraping tool may be rotated. A discharge port for discharging dross is provided at the tip of the automatic scraping means in the traveling direction or the rotating direction. This discharge port is usually sealed and closed, and is opened only when discharging the dross.

Although the essential requirements of the device of the present invention are as described above, the device main body may be configured to be tiltable by the tilting means. This is to increase the filtration efficiency by tilting and facilitate the removal of dross.
In order to obtain the optimum filtration efficiency, the filtration may be performed while changing the angle. The tilting means may use any drive source such as hydraulic pressure, pneumatic pressure, a motor, or the like. It is easy to rotate and incline using a predetermined point as a fulcrum.

This removing apparatus may be used in a batch type by pumping molten zinc containing dross with a ladle or the like, and may be connected to a galvanizing tank for molten zinc by piping to continuously melt molten zinc containing dross by a pump. Zinc may be introduced. Of course, in this case, the filtered zinc is also continuously returned to the plating tank. The introduction pipe and the return pipe can be heated with an electric heater or the like. By doing so, the filtration in the removing device becomes smooth. The degree of heating is 70
About 0 to 750 ° C. is preferable, but it may be lower.
When the dross is removed, the introduction of molten zinc is stopped. Both the introduction of zinc and the return of filtered zinc to the plating tank are connected by piping, and if the main body is tilted, the piping should not come off or be damaged even if tilted. I won't. For example, a flexible type pipe or a slide type connecting portion may be used.

An example of the operating method of this removing apparatus will be described.
Before introducing the dross, the inside of the device is heated to a temperature higher than the melting point of zinc by the gas burner heating means and the heater heating means on the upper part of the device.
The temperature is raised to about 60 ° C or higher. The main body of the apparatus is adjusted by the inclining means so that the carbon filter surface becomes horizontal, and when the dross is introduced, the inclining means gradually inclines the carbon filter surface to increase the contact area between the dross and the carbon filter.

After that, it is heated to 750 ° C. by a heater heating means.
It heats up to a certain degree and promotes the separation of dross and zinc. Zinc in the dross is separated and filtered through a carbon filter. Further, the metal compound in the dross remains on the carbon filter as dross. The dross remaining on the carbon filter is discharged outside the device by the dross scraping means. According to the above dross removing device, zinc can be efficiently separated and recovered from the dross generated in the plating bath. Moreover, the basic unit of plated metal can be improved without pumping out the zinc contained in the dross.

By inclining the main body of the apparatus, the contact area between the carbon filter and the dross is increased, the surface area of the dross itself is increased, and the portion to be heated is increased, so that separation and filtration are promoted. By providing the gas burner heating means and the heater heating means, the dross can be heated to a proper temperature for separation without being naturally cooled, and the separation time is short and efficient separation / filtration can be performed. By providing the dross scraping means, the dross of the metal compound on the carbon filter can be discharged, and the dross can be sequentially separated.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the drawings.

FIG. 1 is a front view showing an example of an embodiment of the device of the present invention. FIG. 2 is a side view of FIG. FIG. 3 is a sectional view of the heater heating means heating device on the outer periphery of the device. The removal device 1 of the present invention comprises a gas burner heating means 2, a heater heating means 3, an actuator 4 for an automatic scraping means,
Actuator 5 for tilting means, zinc receiving bag 6, dross receiving bag 7, carbon filter 8, scraping plate 9,
It is composed of a dross outlet 14 and a column 15.

In this device, a removable carbon filter 8 is attached to the box body at an angle of about 15 degrees,
The gas burner heating means 2 and the heater heating means 3 heat the inside of the apparatus box to about 460 ° C., which is equivalent to the internal temperature of the zinc pot. Before the dross 16 is loaded, the device body 1
Is adjusted by the actuator 5 for the tilting means so that the carbon filter surface becomes horizontal around the fulcrum O on the column 15. When the dross 16 is fed through the charging port 19, the gas burner heating means 2 is stopped, and then the heater. Heating means 3
Thus, in order to promote the separation of the dross 16 and the molten zinc, a mechanism capable of raising the temperature to a predetermined temperature by an automatic temperature control device (not shown) is provided. The tilting actuator 5 gradually raises the angle of the apparatus main body 1 around the fulcrum O on the support column 15 until the carbon filter surface is inclined about 20 degrees from the horizontal angle.

From the zinc-containing dross 16 supplied onto the carbon filter 8, zinc passes through the carbon filter 8 and is separated and filtered. Further, the metal compound in the dross remains on the carbon filter 8 as a residual dross 18. After that, the gas burner heating means at the upper part of the apparatus is operated to heat the residual dross on the filter into a sherbet shape, and then the scraping actuator 4 is actuated downward to scrape off the residual dross 18 remaining on the carbon filter 8. It is discharged from the dross discharge port 14 at.

The separated filtered zinc 17 is collected in the zinc receiving bag 6, and the residual dross 18 is collected in the dross receiving bag 7 from the dross discharge port 14. After that, the scraping actuator 4 is moved upward to move the scraping plate 9 to the upper fixed position.
Back. The operation described above is repeated to separate and recover zinc contained in the dross. Further, with the above-mentioned dross separating and collecting apparatus, the molten zinc contained in the dross can be reliably collected and the basic unit of plated metal zinc can be improved.

The heater heating means shown in FIG. 3 comprises an inner ceramic coating 10, a heater 11, a heat insulating material 12,
The dross 16 does not adhere to the inside of the device due to the inner surface ceramic coating and is insulated by the heat insulating material 12, so that the temperature inside the device does not radiate and the heat can be efficiently raised.

Experimental conditions Filter: Carbon filter (porosity 95-97
%, Pore diameter 3.5-5.0 mm) Heater heating device: Output electric power 11 kW Burner heating device: Combustion capacity 20000 Kca / H Heating temperature: No heating, 500 ° C, 600 ° C, 700 ° C,
750 ° C. The dross removing device shown in FIG. 1 has a porosity of 95 to 97% and a pore diameter.
Equipped with a carbon filter 8 of 3.5 to 5.0mm, without heating inside the removal device, 500 ℃, 600 ℃, 700 ℃, 75
The temperature is set to 0 ° C (the set temperature in the device is the average value of four thermocouples in the device.) The zinc recovery rate is calculated by comparing the amount of separated filtered zinc with the amount of input dross (top dross in this case). The test results obtained are shown in Table 1.

[Table 1]

From the above, the recovery rate is about 50% when the set temperature range in the dross separator is 600 ° C to 750 ° C.
From the test results, it can be seen that the above is the proper temperature.
Further, the carbon filter comprising the porous layer of glassy carbon is excellent in dross separation.

Samples of filtered zinc 17 and residual dross 18 separated and filtered by the dross removing apparatus of FIG. 1 were Fe (%).
Table 2 shows the test results obtained by analyzing each component of Al (%) Pb (%).
Shown in

[Table 2]

As is clear from Table 2 above, the zinc component in the zinc pot has a Fe (%) concentration of 0.034 to 0.036%, and Al.
(%) Concentration 0.147 to 0.172%, Pb (%) concentration 0.003%
However, the Fe (%) concentration of the zinc sample separated and filtered by the top dross separator is in the range of 0.039 to 0.077,
Since the (%) concentration is in the range of 0.152 to 0.215% and the Pb (%) concentration is also <0.001%, the concentration of each component analysis after separation and filtration by the carbon filter 8 in the top dross separation device is extremely low. The effect of the carbon filter 8 is great and the top dross separation is excellent.

The case where the dross separating and collecting apparatus of the present invention is applied to a hot dip galvanizing bath has been described above. The separating and collecting apparatus of the present invention is a hot dip zinc-aluminum alloy plating bath,
It can be applied to other molten plating baths such as a molten aluminum plating bath.

[0032]

As described above, according to the dross separation and recovery apparatus of the present invention, zinc can be efficiently separated and recovered from the zinc contained in the dross generated in the plating bath. Further, metal compounds such as Fe ₂ Al ₅ and ZnO are not returned to the molten zinc bath. Further, it has an extremely beneficial effect that it has an excellent effect that the basic unit of the plated metal can be improved without pumping out the zinc contained in the top dross.

[Brief description of the drawings]

FIG. 1 is a front view showing an example of an embodiment of the device of the present invention.

FIG. 2 is a side view showing an example of an embodiment of the device of the present invention.

FIG. 3 is a cross-sectional view of a heater heating device around the periphery of the device of the present invention.

[Explanation of symbols]

 1 Device Main Body 2 Gas Burner Heating Device 3 Heater Heating Device 4 Actuator for Scratching Means 5 Actuator for Tilt Means 6 Zinc Receiving Back 7 Dross Receiving Back 8 Carbon Filter 9 Scraping Plate 10 Inner Ceramic Coating 11 Heater Heating Means 12 Insulation 13 Cover 14 Dross discharge port 15 Strut 16 Top dross 17 Filtration zinc 18 Residual dross 19 Input port

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Soda 4-533 Kitahama, Chuo-ku, Osaka City Sumitomo Metal Industries Co., Ltd. (72) Tsutomu Takahashi 4-53-3 Kitahama, Chuo-ku, Osaka City No. In Sumitomo Metal Industries, Ltd. (72) Inventor Hiroshi Yasuhiko 4-53, Kitahama, Chuo-ku, Osaka City Sumitomo Metal Industries, Ltd.

Claims (3)

[Claims] 1. A device for removing dross from molten zinc containing dross, comprising a removable carbon filter, a heating means, and an automatic scraping means, and a dross removing device in hot dip galvanizing. 2. The dross removing device for hot dip galvanizing according to claim 1, further comprising an inclining means for inclining the device body. 3. The heating means is a gas burner heating means in the upper part of the apparatus body and a heater heating means in the outer circumference of the apparatus.
Or a dross removing device in hot dip galvanizing according to 2.