JP3029373B2 - Recovery method of zinc chloride from zinc dross - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for recovering high-purity zinc chloride from zinc dross and using the recovered zinc chloride as a raw material for composite iron oxide for soft ferrite.

[0002]

2. Description of the Related Art Conventionally, when a composite iron oxide containing zinc is produced by an oxidative roasting method, a zinc aqueous solution is prepared by dissolving zinc metal or zinc chloride as a zinc source in hydrochloric acid. Raw materials added to aqueous chloride solutions of other constituent metal salts were used. Since zinc raw materials require high purity, expensive zinc oxide or metallic zinc had to be used.
Therefore, a proposal has been made for dissolving zinc ore in hydrochloric acid as an inexpensive zinc raw material to form a chloride solution (JP-A-5-43249). Zinc in the zinc ore exists as ZnSO ₄ ,
The oxidized and roasted product is in the form of ZnO. In the former case, since S, which is harmful to ferrite, remains in the solution, a complicated process is required for its purification. When using the latter,
The solubility of ZnO in hydrochloric acid is high only when the pH value is low, and there is a disadvantage that excessive free hydrochloric acid is required for dissolving ZnO, so that the production cost increases.

On the other hand, when a composite iron oxide is produced by spraying and roasting a chloride aqueous solution containing zinc chloride, zinc chloride having a high vapor pressure evaporates and evaporates, and the recovery rate of the zinc content in the generated iron oxide is reduced. Was a big challenge. In contrast,
Japanese Patent Application Laid-Open No. 4-206606 proposes a technique in which the zinc content is stabilized as zinc oxide by adjusting the pH of an aqueous metal chloride solution, and the zinc content is not volatilized in the roasting process. According to this method, since the zinc component is dispersed as a solid in the aqueous solution, there is a disadvantage that the zinc component in the product iron oxide is not sufficiently uniformly dispersed. Moreover, since the zinc oxide to be added is fine particles of high purity, the raw material cost increases.

[0004]

The inventor of the present invention has invented a method capable of roasting a uniform composite iron oxide even when zinc is dissolved as an aqueous solution of chloride in an aqueous solution of another metal chloride. No. 5-94912). Therefore, the present invention proposes a method for purifying zinc chloride required as a raw material of composite iron oxide from inexpensive zinc dross. Until now,
Since zinc dross discharged from the galvanizing process of steel sheet contains Pb, Al, Si, Cr, etc. in addition to zinc,
It was inappropriate as a high-purity zinc raw material and was disposed of as a crude zinc raw material.

[0005]

The inventors of the present invention have studied whether or not the above zinc dross is a raw material for zinc chloride. As a result, the zinc dross contained 95 to 99% of Zn, 0.5 to 2.5% of Fe, and 0.1 to 2% of Al. .
5%, other 1.0% (all wt%), extremely high zinc content of 95% or more, easily soluble in hydrochloric acid, and capable of purification by removing impurities by adjusting the pH of aqueous solution Using this principle, a method for purifying a high-purity aqueous solution of iron-zinc chloride or an aqueous solution of zinc chloride was developed. In the present specification, zinc chloride is a concept that includes not only solid zinc chloride but also zinc chloride containing iron and dissolved in an aqueous solution.

(1) A first aspect of the present invention is a method for recovering zinc chloride from zinc dross, comprising the following steps. (A) a step of dissolving zinc dross generated during galvanizing a steel sheet in an aqueous hydrochloric acid solution; and (b) adding an alkaline agent to the aqueous chloride solution obtained by the dissolution to adjust the pH to 4 or more and 6 or less. And further adding one or two of an anionic flocculant, a nonionic flocculant or a cationic flocculant, and aggregating / precipitating the impurities to separate them. (C) separating the aggregated / precipitated impurities Recovering zinc chloride from the purified chloride aqueous solution.

(2) A second aspect of the present invention is the above-mentioned pH of 4
In place of the range of not less than 6 and not more than 6,
A method for recovering zinc chloride, wherein the method is adjusted to a range of H4.5 to 5.5.

(3) A third aspect of the present invention is the above-mentioned coagulation / sedimentation.
A method for recovering zinc chloride, wherein the impurities are separated by a centrifugal separator .

A method of using zinc chloride recovered by the method according to any one of the above-mentioned embodiments as a raw material of a composite iron oxide for soft ferrite.

[0010]

First, zinc dross is dissolved in an aqueous hydrochloric acid solution. An alkaline aqueous solution such as ammonia is added thereto, and the pH value is increased to 4.5-5.5 with stirring. When the solution is allowed to stand after the pH has reached a predetermined value, metal impurities such as Al crystallize in the solution as hydroxide particles, and non-metal impurities such as Si co-adsorb with the metal hydroxide. FIG. 2 shows the relationship between the pH value of the aqueous solution and the concentrations of zinc and impurities at this time.
When the pH value is 4 or more, a high-purity aqueous solution of iron-zinc chloride, which is an object of the present invention, is obtained. However, when the pH value exceeds 4.5, impurities such as Al and Si are almost completely crystallized. It is shown.

It is also shown that when the pH value exceeds 6, zinc also crystallizes as chloride. To condense the crystallized impurities, one of a commercially available anionic or nonionic flocculant, or a cationic flocculant, or 2
The seeds are added to agglomerate, precipitate and separate these oxides to obtain a high-purity iron-zinc chloride aqueous solution. Further, when zinc chloride is separated from this aqueous solution, high-purity iron-zinc chloride can be obtained. This iron-zinc chloride aqueous solution can be used as a zinc raw material for soft ferrite as it is. Regarding the method for producing soft ferrite, the applicants have
The manufacturing method disclosed in Japanese Patent Application Laid-Open Publication No. H10-205163 may be used.

[0012]

Embodiments of the present invention will be described below.
FIG. 1 is a schematic diagram showing an example of an apparatus for performing the method of the present invention. A hydrochloric acid aqueous solution 2 and a zinc dross (zinc source) 3 are put into a dissolution tank 1, and these are stirred by a stirrer 4. Thus, the zinc source 3 is dissolved in hydrochloric acid to form a solution. This solution is supplied to the pH adjusting tank 6 by the pump 5. The solution pH in the pH control tank 6 is usually around 2.5,
It is measured by the pH meter 7. The solution in the pH control tank 6 is stirred by a stirrer 8 and an alkaline substance 9 such as NH ₄ OH
Is added to adjust the pH to a predetermined value in the range of 4.5-5.5.

At the stage when the pH is adjusted, a crystallization reaction of Al hydroxide occurs. An anionic or nonionic coagulant 12 is added to this to coagulate the crystallized product. Aggregates of the liquid discharged from the pH adjusting tank 6 are settled and separated by the thickener 13, and the supernatant liquid is further filtered by the filter 14. Alternatively, the above-mentioned discharged liquid can be separated into solid and liquid by the centrifugal separator 15. As a result, a high-purity iron-zinc chloride aqueous solution is obtained. Note that lead, which is an impurity, precipitates in the dissolution tank 1 without being dissolved in hydrochloric acid. Dissolution tank 1
Inside, a dissolution reaction or hydrogen gas is generated, and this hydrogen gas can be separately recovered and reused. Next, specific examples will be described.

Example 1 65 kg of zinc dross cut to a particle size of 5 to 10 mm was treated with hydrochloric acid 34
Dissolved in 0 l (18% HCl). Table 1 shows the chemical composition of the zinc dross used. After dissolution, stirring and N
Adjust the pH to 4.5-5.5 with H ₄ OH (0.1% NH ₃ ),
The aggregate was precipitated by adding 25 ppm of a nonionic flocculant, and the supernatant was filtered. The analytical values of the filtrate are shown in Table 2. From this result, by removing impurities according to the present invention, Al becomes 0.01% or less, Pb becomes a trace, and
It was confirmed that 99% or more and other impurities were removed by 100%. If the pH is 6 or more, zinc chloride is crystallized, and the yield of zinc is remarkably reduced.

[0015]

[Table 1]

[0016]

[Table 2]

Example 2 The same operation as in Example 1 was performed, and zinc chloride was recovered using a centrifugal separator for separating aggregated particles. In Example 1, it took 1-2 hours for sedimentation of aggregates, whereas centrifugation took 5 hours.
The separation of solid and liquid was possible in minutes.

[0018]

According to the present invention, high-purity and inexpensive zinc raw materials can be supplied from unused zinc dross instead of expensive zinc raw materials. This zinc raw material can be used as a zinc raw material for soft ferrite.

[Brief description of the drawings]

FIG. 1 is a diagram showing an apparatus for carrying out the present invention.

FIG. 2 is a diagram showing the pH of a chloride aqueous solution in which zinc dross is dissolved and the residual ratio of impurities in the solution.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tetsuya Watanabe 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Steel Pipe Mining Co., Ltd. (72) Inventor Yoshiki Shibuya 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Steel Pipe Mining (72) Inventor Tatsuo Inoue 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Steel Pipe Mining Co., Ltd. (72) Inventor Katsuhiro Nishi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Steel Pipe Mining Co., Ltd. 72) Inventor Yutaka Yoshioka 2--11 Kanda Nishikicho, Chiyoda-ku, Tokyo Inside iRocks NKK Inc. (72) Inventor Tomoo Maeda 1-2-1, Marunouchi 1-chome, Marunouchi, Chiyoda-ku, Tokyo (56) Reference Document JP-A-2-172820 (JP, A) JP-A-63-166719 (JP, A) JP-A-5-43249 (JP, A) (58) Survey The field (Int.Cl. ^7, DB name) C01G 9/04 H01F 1/36

Claims (4)

(57) [Claims] 1. A method for recovering zinc chloride from zinc dross, comprising the following steps: (A) a step of dissolving zinc dross generated during galvanizing a steel sheet in an aqueous hydrochloric acid solution; and (b) adding an alkaline agent to the aqueous chloride solution obtained by the dissolution to adjust the pH to 4 or more and 6 or less. And further adding one or two of an anionic flocculant, a nonionic flocculant or a cationic flocculant, and aggregating / precipitating the impurities to separate them. (C) separating the aggregated / precipitated impurities Recovering zinc chloride from the purified chloride aqueous solution. 2. The method according to claim 1, wherein said pH is in the range of 4 to 6.
The method for recovering zinc chloride according to claim 1, wherein the pH is adjusted to a range of 4.5 to 5.5 by adding an alkaline agent. 3. A centrifugal separator for separating the aggregated and precipitated impurities.
The method for recovering zinc chloride according to claim 1 or 2, wherein the zinc chloride is separated . 4. A method of using zinc chloride recovered by <br/> method according to any one of claims 1 to 3 as a raw material of the composite iron oxide for soft ferrites.