JP2816293B2 - Zinc oxide with excellent pneumatic transportability and its production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to zinc oxide used for supplying zinc ions to a plating solution in a continuous electrogalvanizing of a metal strip using an insoluble anode, and a method for producing the same. .

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for improved corrosion resistance in automobiles, home electric appliances and the like, and in addition to conventionally used galvanized steel sheets, there has been a demand for recently developed alloy-coated steel sheets such as zinc-nickel plated steel sheets. Has also increased significantly. In order to cope with such an increase in demand, high-speed plating with a high current density that enables high-efficiency production has been adopted.However, in the high-speed plating, the anode replacement is more required than in the soluble anode method, which requires frequent anode replacement. It goes without saying that a system in which unnecessary metal ions are continuously supplied using an insoluble anode such as an iridium-based one which is unnecessary is advantageous.

As a plating solution, a sulfuric acid-based electrolytic solution is usually used. In addition, as a method of replenishing zinc ions in the plating solution, there are a method of dissolving metal zinc by directly contacting the plating solution and a method of dissolving a metal compound such as zinc oxide. Since the method of directly dissolving granular or massive metallic zinc has a low dissolution rate, it is more efficient to dissolve a powdered zinc compound.
According to Japanese Patent Application Laid-Open No. 58-13639, it is described that zinc oxide or a basic salt in a powder state is previously dispersed in water and then charged into a plating bath.

[0004] In addition, zinc oxide may be dissolved in alkali as a phosphating solution. When zinc carbonate alone or a mixture, or a mixture of these and zinc oxide, is directly poured into an acid or alkali solution, the heat of reaction generated on the powder surface tends to cause agglomeration (blocking), and the agglomerated material hardly dissolves. There are drawbacks. Tokiko
The method according to JP-A-58-13639 improves this point by dispersing in water and prevents agglomeration, but requires a high-speed stirrer (homogenizer) or the like for dispersion treatment, Excessive supply of water requires a means of removing water such as an evaporator, and iron ions in the plating solution eluted from the steel plate are oxidized by depositing as hydroxide on the surface of zinc oxide depending on the pH of the solution. There are problems such as hindering dissolution of zinc.

[0005] The zinc oxide powder is usually packed and shipped in a bag-like container such as a flexible container, and the zinc oxide powder is received and stored in a hopper provided in a manufacturing facility. Is common. Then, when receiving the hopper, the contents of the bag-shaped container such as a flexible container hung by a crane or the like are untied and the contents are dropped. It is dangerous work because you will enter.

[0006] The transfer from the hopper to the next step, for example, a dissolving tank or a mixing tank, is usually performed by a conveyor. There is a problem that intrusion into the part causes troubles such as wear and poor lubrication.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a zinc oxide excellent in pneumatic transportability which solves such a problem associated with transport by improving the form of the powder.

[0008]

Means for Solving the Problems The zinc oxide excellent in air transportability of the present invention has a compressibility of 50% or less and an average particle size of 50 μm.
It is characterized by being granulated as described above. In addition, the method for producing zinc oxide of the present invention is characterized in that a granule is granulated with a pan pelletizer without using a binder, the compression degree is 50% or less, and the average particle diameter is 50 μm.
Either the above granules, or granules with a pelletizer using a binder and a compression degree of 50% or less and granules with an average particle diameter of 50 μm or more, or a pulverized mass with a compression degree of 50% or less It is characterized by being in the form of granules having an average particle size of 50 μm or more.

[0009]

[Action] In the case of granular zinc oxide, if the degree of compression exceeds 50%, the powder is clogged at the bent portion of the pipe, etc., and it is difficult to transport air. Incidentally, the degree of compression is defined by the following equation. Compressibility = (tap density−bulk density) / tap density The tap density is the density in a state of being vibrated or compacted and sufficiently compressed.

On the other hand, when the average particle size is less than 50 μm, troubles such as dust generation, leakage, clogging, etc. occur as in the case of powder, and no improvement effect is recognized. As described above, in the present invention, the zinc oxide powder is formed into granules having a degree of compression of 50% or less and an average particle size of 50 μm or more. On the other hand, the upper limit of the particle size is not particularly limited in terms of transportability,
Unnecessarily increasing the size is wasteful in terms of cost in the granulation process, and thus naturally has a limit. In addition, since it is preferable that the particle size is not too large when dissolving in the next step, it is realistic to set the upper limit to about 5 mm.

[0011]

EXAMPLE An example of the zinc oxide excellent in air transportability of the present invention will be described. FIG. 1 shows the result of pneumatic transportation of granular zinc oxide (zinc white according to the French method, JIS special product) with varying degrees of compression. First, as experimental conditions, the pipe diameter was 100 mm, the transport height was 20 m, and the pressure was 1.9 kgf / c as the air source.
An air transport vehicle with m ² and a flow rate of 5.2 Nm ³ / min was used, and the transport destination was opened to the atmosphere with a hopper provided with a bag filter. A pneumatic transport vehicle is a special lorry vehicle that has a compressor mounted on the vehicle and can directly transport pulverized materials in the tank to receiving equipment on the ground.

As shown in FIG. 1, pneumatic transportation was difficult when the degree of compression exceeded 50%. Such granular zinc oxide can be produced by granulating without a granulation nucleus or a binder using a pan pelletizer. In the case of using a pump pelletizer, as shown in FIG. 1, the degree of compression and the average particle diameter are in inverse proportion. In addition, there are various methods such as an extrusion molding method, a crushing method, and a dry spraying method in addition to a pan pelletizer for the granulation method. In the case of zinc oxide, the pelletizer is the easiest and most efficient method.

In general, a binder is often used, but any binder may be used as long as it does not adversely affect electroplating and plated products, but the zinc oxide fine powder itself adheres to each other. It is easy to granulate without using a binder. In the case of the pan pelletizer method, the size of the granules to be taken out can be arbitrarily changed by adjusting the rotation speed or the inclination angle of the bread. It goes without saying that the minimum and maximum diameters of the granules to be used can be arbitrarily controlled by sieving.

In order to dissolve such a granular zinc oxide in an acid or an alkali, the zinc oxide is dispersed once in water,
There is no need to use a powerful stirrer at all, and it can be easily dissolved by simply adding it directly.

[0015]

By using the granular zinc oxide of the present invention, it is possible to receive the air directly from the air carrier to the hopper by air transport without using a flexible container, and to generate dust and other environmental problems. It has many excellent effects, such as eliminating dangerous work.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of an air transport experiment of granular zinc oxide of the present invention.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Sakurai 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Pref. Chome (without address) Inside Kawasaki Steel Corporation Mizushima Works (72) Inventor Shingo Fujii 1-chome, Mizushima Kawasaki-dori (Kurashiki City, Okayama Prefecture) Kawasaki Steel Corporation Inside Mizushima Steel Works (56) -23797 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C01G 1/00-57/00

Claims (4)

(57) [Claims] 1. A zinc oxide excellent in air transportability, characterized by being granulated into a granule having a degree of compression of 50% or less and an average particle size of 50 μm or more. 2. A method for producing zinc oxide excellent in pneumatic transport, characterized by granulating with a pan pelletizer without using a binder to form granules having a compression degree of 50% or less and an average particle diameter of 50 μm or more. 3. A method for producing zinc oxide excellent in pneumatic transport characteristics, wherein the zinc oxide is granulated by a pan pelletizer using a binder to form granules having a compression degree of 50% or less and an average particle diameter of 50 μm or more. 4. A method for producing zinc oxide having excellent pneumatic transport properties, characterized by pulverizing a lump into granules having a degree of compression of 50% or less and an average particle diameter of 50 μm or more.