JPH10330859A - Zinc recovering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive zinc recovering device which recovers zinc from top dross. SOLUTION: This device has a dross housing case 1 which is disposed in a galvanizing bath 3 vessel for applying galvanizing on a steel strip 4 and has apertures 12 of 1 to 50 mm in diameter to drop the zinc on a bottom housing the top dross 5 or further flanks and a heat retaining means 13 which is capable of holding the dross at a tap. above the m.p. of the zinc. The bottom of the dross housing case 1 is preferably made exchangeable. The zinc recovering device 2 may be disposed freely movably forward and backward above the galvanizing bath 3 vessel for executing the galvanizing or in the galvanizing bath.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc recovery apparatus for recovering useful zinc present in a top dross generated in a hot dip galvanizing bath for hot dip galvanizing a steel strip.

[0002]

2. Description of the Related Art Generally, in a hot-dip galvanizing bath, iron is eluted from a passing steel strip and partially reacts with zinc in the galvanizing bath.
FeZn ₇ is formed and deposited on the bottom of the plating bath. In addition, the zinc drawn up by the steel strip is air-oxidized when refluxed to the plating bath, forming a muddy material mixed with metallic zinc, and the iron reacting with Al or FeZn ₇ in the zinc plating bath is Fe ₂ Al ₅
As a result, it floats on the galvanizing bath to generate top dross. For this reason, at the time of manufacturing a hot-dip galvanized steel sheet, the top dross in the hot-dip galvanizing bath is periodically discharged out of the bath to prevent the top dross from adhering to the steel sheet.
However, the molten zinc is discharged together with the dross, significantly deteriorating the zinc unit consumption in the production of plated steel sheets.

As a method for recovering zinc, there is a method in which dross is heated to a temperature higher than the boiling point of zinc to vaporize and recover zinc (Japanese Patent Laid-Open No.
292451), a method in which zinc metal in dross is heated and melted at a high temperature (see JP-A-4-32544), and a method in which a recovery aid is added to chemically recover zinc from dross (Japanese Patent Laid-Open No. 63-63). -58224).

[0004]

SUMMARY OF THE INVENTION
In the technique described in JP-A-7-292451, it is necessary to heat dross to a temperature higher than the boiling point of zinc by a heating evaporator outside the plating bath, and a large-scale heating device is required. It is necessary to use a material in consideration of airtightness or reactivity with zinc for the vaporization conduit leading to the furnace, and there is a problem in that extremely expensive equipment such as a heating distillation apparatus and a vaporization conduit is required. According to the technique described in Japanese Patent Application Laid-Open No. 4-32544, solid or semi-molten zinc is remelted at a high temperature of 750 ° C. and a container having a mesh bottom is used. Effluent and the efficiency of separation and recovery of zinc metal from dross is low.

Further, in the technique described in Japanese Patent Application Laid-Open No. 63-58224, an expensive recovery aid is added, so that the cost of recovering zinc is extremely expensive, and the equipment is large. Become. An object of the present invention is to solve the above-mentioned problems and to provide an inexpensive apparatus that can easily recover zinc from top dross.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the top dross is a high-concentration solid-liquid in which high-concentration solid particles dross are mixed in liquid zinc. I came to the conclusion that it should be considered a mixed fluid (non-Newtonian fluid). When a liquid is filtered from a solid-liquid mixed fluid having a high solid concentration using a filter medium, solid particles are cross-linked and deposited on the filter medium surface, and the filtration proceeds while acting as a filter medium in the subsequent filtration, so-called cake filtration is achieved. It is done. Based on this idea, if cake filtration is achieved, it is thought that filtration separation can be performed using a filter medium with a filter medium pore diameter larger than the solid phase particle diameter. It has been found that by filtering using a filter medium having the same, zinc can be efficiently dropped and extracted without dross falling from the filter medium hole.

The present invention has been made based on the above findings. That is, the present invention is a zinc recovery device disposed in a hot-dip galvanizing bath for applying hot-dip galvanizing to a steel strip, and a dross storage case for storing top dross generated in the hot-dip galvanizing bath, A heat retaining means for retaining the stored top dross, wherein the dross storage case is provided with a plurality of openings having a minimum diameter of 1 to 50 mm for collecting and dropping zinc at the bottom or the side surface. It is preferable that the dross storage case and the heat retaining means are disposed on the hot-dip galvanizing bath so as to be able to advance and retreat. Further, in the present invention, the dross storage case is immersed and disposed in the hot-dip galvanizing bath together with a zinc recovery case that is provided immediately below the dross storage case and recovers zinc dripped from the dross storage case. The heating means may be a hot-dip galvanizing bath.

In the present invention, it is preferable that the bottom of the dross storage case has a plurality of openings and an opening area ratio is 1 to 70%, and it is preferable that the bottom is replaceable.

[0009]

FIG. 1 shows an embodiment of the apparatus according to the present invention. FIG. 1 shows a hot-dip galvanizing bath in a continuous hot-dip galvanizing line. The steel strip 4 treated in the annealing furnace (not shown) is guided to the hot-dip galvanizing bath 3 without being exposed to the atmosphere by the snout 7, its traveling direction is changed by the sink roll 6, and is pulled upward through the guide roll. . After leaving the hot-dip galvanizing bath 3, in order to squeeze out excess zinc, a high-pressure gas is blown by a coating amount control nozzle 10 to adjust the coating amount.

Usually, the top dross generated in the hot-dip galvanizing bath is periodically discharged out of the bath to prevent the top dross from adhering to the steel sheet. In the present invention, the top dross 5 generated in a hot-dip galvanizing bath for hot-dip galvanizing a steel strip is pumped out and stored in a zinc recovery device 2 disposed in a hot-dip galvanizing bath. The zinc recovery device 2 may be provided on a hot-dip galvanizing bath or may be immersed in the hot-dip galvanizing bath.

First, description will be made of a case of disposing a hot-dip galvanizing bath. In FIG. 1, the zinc recovery device 2 is disposed freely on a hot-dip galvanizing bath. The zinc recovery device is made freely movable on rails or the like by a moving means (not shown). When recovering zinc from dross, the zinc recovery device moves to a hot-dip galvanizing bath, and in other cases, retreats from the hot-dip galvanizing bath.

The zinc recovery apparatus 2 has a dross storage case 1 made of steel or ceramic. A plurality of openings 12 are formed in the bottom and side surfaces of the dross storage case 1 so that the collected zinc 8 can be dropped.
The opening 12 may be circular or slit-shaped. The cross section of the aperture may be, for example, either a tapered cross section or a vertical cross section, as shown in FIG. 2, and the minimum diameter (width) d is in the range of 1 to 50 mm. The minimum diameter is related to the holding temperature and the holding time at the time of collection. Here, FIG.
The present inventors have found that the effect of the opening diameter on the zinc recovery efficiency from the top dross when the top dross is housed in dross storage cases having different opening diameters and is kept at 460 ° C. for 90 minutes is shown. is there. Diameter (width) of the smallest part of the opening
If it is less than 1 mm, as shown in FIG. 3, the openings are significantly blocked, and the recovery efficiency is reduced to 20% or less. As the hole diameter increases, the recovery efficiency of zinc improves, and the hole diameter is 10 mm.
In the above cases, it is as high as 80%. On the other hand, if the diameter (width) of the minimum portion of the opening exceeds 50 mm, dross flows out of the opening. For this reason, the minimum diameter (width) of the opening is limited to 1 to 50 mm. It is more preferably from 10 mm to 50 mm.

The bottom of the dross housing case 1 is provided with a plurality of openings in the range of 1 to 50 mm, and the opening area ratio of the bottom (opening area / bottom area) is in the range of 1 to 70%. It is preferable to select the number of holes and the diameter of the holes. Open area ratio is 1
If it is less than%, filtration is possible, but the separation is too time-consuming and inefficient. On the other hand, if it exceeds 70%, it takes a long time to reach a steady state of cake filtration, and at the start of filtration and separation, dross flows out of the opening and easily mixes into the molten zinc.

The dross housing case 1 is preferably made of steel or ceramic, or steel whose surface is sprayed with carbon and ceramic. When the dross housing case 1 is made of steel, the holes provided on the bottom and side surfaces may be significantly melted and damaged by the outflow of zinc. For this reason, it is preferable to make the bottom part replaceable, prepare a replacement bottom plate 14 for a dross storage case as shown in FIG. 4, and replace it appropriately. As a result, the operation can be continued without newly manufacturing the entire dross storage case, and the collection efficiency can be improved. Needless to say, the exchange bottom plate is provided with a plurality of openings.

The zinc recovery device 2 includes a dross storage case 1
A heat retaining means 13 is disposed near the outside of the container so that the dross can be maintained at a predetermined temperature equal to or higher than the melting point of zinc. In FIG. 1, the burner 9 is shown as the heat retaining means 13, but it is not limited to this. It suffices that any amount of heat can be supplied that can compensate for the temperature drop of the dross and can maintain the temperature at or above the melting point of zinc, and any means such as an electric heating plate may be used.

The housed top dross is at a temperature equal to (about 460 ° C.) or slightly lower than the plating bath temperature, and is maintained at a temperature approximately equal to or higher than the melting point of zinc at the plating bath temperature. When the size of the hole is 1 mm or more in the minimum hole diameter, the molten zinc attached to the dross is transmitted through the gap of the dross and can be dropped from the opening. By maintaining the temperature at 700 ° C or lower, when the size of the opening at the bottom of the dross housing case is 50 mm or less in the minimum hole diameter, the molten zinc attached to the dross passes through the gap of the dross and drops from the opening.

The molten zinc dropped from the opening 12 is preferably allowed to flow directly into a galvanizing bath. Next, a case where the zinc recovery apparatus is immersed in a hot dip galvanizing bath will be described with reference to FIG. In FIG. 5, the zinc recovery device 2
It is immersed in the hot-dip galvanizing bath 3. The zinc recovery apparatus 2 is a steel dross storage case 1 provided directly below the dross storage case 1 and a dross storage case 1 made of steel or ceramic or a steel made by spraying carbon and ceramic on the surface. And a recovery zinc case 2a. The dross storage case 1 has the same shape as the case where it is disposed on the hot-dip galvanizing bath, and there is no inconvenience. It is preferable that the case upper surface of the zinc recovery case 2a and the plating bath surface be substantially at the same level from the viewpoint of facilitating dross recovery.

The shape of the zinc recovery case 2a is not particularly limited as long as it can store zinc in which zinc is dropped from the dross storage case. Pressurizing duct 17 inside the zinc recovery case to make it easier to drip zinc from the dross storage case
, The pressure may be slightly reduced, and a structure capable of reducing the pressure is preferable. In addition, zinc recovery case 2a
Is preferably made of the same material as the above-mentioned dross housing case.

It is preferable that the recovered zinc 8 is returned to the bath by a pump 16 or the like from a pipe 15 provided in the zinc recovery case 2a. The dross in the dross storage case is replaced as soon as the case is full. It is preferable that the dross housing case 1 has a replaceable structure, and it is preferable that the dross housing case 1 can be separated and joined to the zinc recovery case 2a.

In FIG. 5, as a dross heat retaining means, a hot dip galvanizing bath is used as a heat source for keeping heat. Thus, heat radiation from the dross storage case is suppressed, and no special heat source is required.

[0021]

Embodiments of the present invention will be described below. (Example 1) A zinc recovery apparatus 2 pumped out of a top dross in a hot-dip galvanizing bath for hot-dip galvanizing a steel strip and disposed on a hot-dip galvanizing bath 3 shown in FIG.
Was housed in the dross housing case 1 inside. The top dross was stored by a conventional large spoon-shaped jig having an opening, and the stored top dross weighed 200 kg.

After accommodating the top dross, the dross is heated to a temperature higher than the melting point of zinc at about 700 ° C.
For 20 minutes. The dross storage case 1 installed in the zinc recovery apparatus 2 is provided with a circular zinc extraction hole having a diameter of 20 mm (a total of 6 holes, bottom opening area ratio: 10%) as the opening 12. 12 to 160 kg of zinc was recovered (recovery rate
80%).

The amounts of Fe and Al contained in the recovered zinc are 0.053 wt% and 0.167 wt%, respectively.
Fe and Al contents are significantly lower than 1.10 wt% and 1.52 wt%, respectively, and zinc bath components (Fe content: 0.040 wt%, Al content: 0.14 wt%)
0 wt%). Although the recovered zinc was directly flowed into the zinc bath, a good product was obtained without contaminating the zinc bath. (Example 2) Top dross floating in a hot-dip galvanizing bath for hot-dip galvanizing a steel strip in the same manner as in Example 1.
150 kg was pumped out, stored in a dross storage case 1 in a zinc recovery apparatus immersed and disposed in a hot dip galvanizing bath shown in FIG. 5, and kept at the same temperature of 460 ° C. as the hot dip galvanizing bath for 90 minutes.

The dross storage case 1 installed in the zinc recovery apparatus 2 is provided with a 35 mm-diameter circular zinc extraction hole (a total of 4 holes, opening area ratio: 7%) as an opening. 120 kg of zinc was recovered from the holes (recovery rate 80%). Also,
The amounts of Fe and Al contained in the recovered zinc are 0.049 wt%, respectively.
0.159wt%, each of Fe and Al content of top dross
It was overwhelmingly lower than 1.02 wt% and 1.41 wt%, and was almost equivalent to zinc bath components (Fe content: 0.040 wt%, Al content: 0.140 wt%).

Although the recovered zinc 8 was directly flowed into the zinc bath, a good product was obtained without contaminating the zinc bath.

[0026]

According to the present invention, zinc, which has been discharged together with the top dross, can be recovered with high efficiency by means of inexpensive simple equipment, and it is possible to reduce the basic unit of zinc during the production of hot-dip galvanized steel sheet. It has a remarkable industrial effect.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing one embodiment of the device of the present invention.

FIG. 2 is a cross-sectional view showing a cross-sectional shape of an opening at the bottom of the dross housing case.

FIG. 3 is a graph showing the effect of the opening diameter at the bottom of the dross storage case on the zinc recovery efficiency.

FIG. 4 is a conceptual diagram showing a shape of a replacement bottom plate for a dross storage case.

FIG. 5 is a sectional view schematically showing one embodiment of the device of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Dross storage case 2 Zinc recovery device 2a Zinc recovery case 3 Hot dip galvanizing bath 4 Steel strip 5 Top dross 6 Sink roll 7 Snout 8 Recovered zinc 9 Burner 10 Adhesion control nozzle 11 Guide roll 12 Opening 13 Heat retention means 14 Replacement bottom plate for dross storage case 15 Piping 16 Pump 17 Pressure release duct

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shin Arai 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Chiba Works, Ltd. (72) Inventor Masayuki Kageyama 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki (72) Inventor Yasuo Kobayashi 1st Kawasaki-cho, Chuo-ku, Chiba City, Chiba Pref.

Claims (5)

[Claims] 1. A zinc recovery apparatus disposed in a hot-dip galvanizing bath for applying hot-dip galvanizing to a steel strip, comprising: a dross housing case for housing top dross generated in the hot-dip galvanizing bath; Heat retaining means for retaining the heated top dross, and the dross storage case is provided with a plurality of apertures having a minimum diameter of 1 to 50 mm for collecting and dropping zinc on the bottom or the side surface. Characterized zinc recovery equipment. 2. A zinc recovery apparatus according to claim 1, wherein said dross storage case and said heat retaining means are disposed on said hot-dip galvanizing bath so as to be able to advance and retreat. 3. The dross storage case is immersed and disposed in the hot-dip galvanizing bath together with a zinc recovery case that is provided immediately below the dross storage case and recovers zinc dripped from the dross storage case. The zinc recovery apparatus according to claim 1, wherein the means is a hot-dip galvanizing bath. 4. The zinc recovery apparatus according to claim 1, wherein the bottom of the dross storage case has a plurality of openings and an opening area ratio is 1 to 70%. . 5. The zinc recovery apparatus according to claim 1, wherein the bottom of the dross storage case is a replaceable bottom.