JP2003096588A - Method of manufacturing high-purity metal magnesium and method of manufacturing high-purity titanium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing high-purity metal magnesium which is less contaminated with nickel and a method of manufacturing high- purity titanium using the same as raw material. SOLUTION: The metal magnesium existing in the magnesium chloride by- produced in a process step for manufacturing titanium by a Kurrol's method is removed and thereafter the high-purity metal magnesium is obtained by electrolytically refining this magnesium chloride. This high-purity metal magnesium is used as a raw material and titanium tetrachoride is reacted with the high-purity metal magnesium, by which the high-purity titanium is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing high-purity metallic magnesium and a method for producing high-purity titanium using the same as a raw material.

[0002]

2. Description of the Related Art In recent years, with the development of LSI technology, the demand for high purity semiconductors and the like has been increasing, and titanium materials, which are in high demand as barrier materials and target materials, have also been highly purified. It has been demanded. High-purity titanium materials for such electronic materials include Fe, Ni, C
The upper limit of the content of the impurity component such as r, Al, V, O is set. Of these impurities, nickel is a few pp
There is a strict standard of less than m. Therefore,
When manufacturing sponge titanium for high-purity titanium material, an apparatus and a process different from the usual process are adopted.

[0003]

In the process of producing titanium sponge by the Kroll method, impurities such as nickel are mixed in titanium sponge mainly due to stainless steel which is a material of the reducing container. Impurities are unevenly distributed on the outside of the lump, and in order to obtain high-purity titanium, only the central part of the sponge titanium lump with less pollution is collected, and a layer of mild steel with a low nickel content is placed on the inner surface of the reduction container. The means of providing it was adopted.
However, even if the above-mentioned measures are taken, impurities, especially the nickel component in titanium, are not reduced, and further improvement in the production process of titanium by the Kroll method has been desired.

On the other hand, with respect to metallic magnesium used as a reducing agent for titanium tetrachloride, magnesium chloride produced as a by-product in the process of producing titanium sponge for reducing titanium tetrachloride with metallic magnesium is refined by electrolytic refining and is recycled. In this metallic magnesium, nickel of 100 ppm dissolved in the reducing container or other factors was dissolved, which was also a major cause of contamination of titanium sponge. Therefore, how to produce high-purity metallic magnesium with few impurities and use this for producing titanium has been an issue for producing high-purity titanium containing less nickel.

Therefore, an object of the present invention is to provide a method for producing high-purity metallic magnesium with less nickel contamination and a method for producing high-purity titanium using the same as a raw material.

[0006]

[Means for Solving the Problems] The inventors of the present invention analyzed the behavior of the nickel component in the metallic magnesium recycling process and conducted extensive studies to achieve the above object. As a result, in the process of recycling metallic magnesium,
In the magnesium chloride produced as a by-product in the reduction step, there exists a state in which metallic magnesium in which nickel is dissolved in a high concentration is suspended, and when such metallic chloride is processed in the electrolytic refining step to produce metallic magnesium, It has been found that almost all nickel content brought into the electrolytic refining process is transferred to the electrolytically produced metallic magnesium. From this, it was found that by removing or reducing as much as possible the metallic magnesium present in the magnesium chloride brought into the electrolytic refining step, metallic magnesium having an extremely small amount of nickel can be produced by electrolytic refining.
Furthermore, they have found that titanium sponge having extremely little nickel can be produced by using this magnesium metal as a reducing agent.

That is, the method for producing high-purity magnesium of the present invention is characterized in that the magnesium magnesium present in the magnesium chloride by-produced in the titanium production step by the Kroll method is removed, and then the magnesium chloride is electrolytically refined. I am trying. Furthermore, the present invention is characterized in that the nickel concentration in the magnesium metal after electrolytic refining is 10 ppm or less. The method for producing high-purity titanium of the present invention is characterized by reacting the high-purity metallic magnesium obtained by the above-mentioned production method with titanium tetrachloride.

In the present invention, the metallic magnesium present in magnesium chloride is removed. This removal not only means the complete removal of the metallic magnesium but also the partial removal thereof. Be done.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments embodying the present invention will be described below. (1) Derivation of Nickel in Produced Metal Magnesium Nickel is mutually dissolved with metal magnesium. Therefore, when it comes into contact with nickel or a metal containing nickel, nickel is diffused into solid solution or dissolved in metal magnesium. Since nickel that has once transferred to metallic magnesium dissolves in metallic magnesium, it is difficult to separate and remove only nickel. On the other hand, since nickel is hardly dissolved in magnesium chloride, most of the nickel in the metal magnesium produced in the electrolytic refining process is considered to be derived from nickel in the metal magnesium present in the magnesium chloride supplied to the electrolytic cell. To be Therefore, in order to reduce the amount of nickel in the magnesium metal produced in the electrolysis step, it is effective to reduce the amount of metallic magnesium in the raw material magnesium chloride.

(2) Existence form of metallic magnesium in magnesium chloride Unreacted metallic magnesium exists in the form of droplets in the molten magnesium chloride transferred from the reduction step to the electrolytic refining step. Here, since the specific gravity of metallic magnesium is slightly smaller than that of magnesium chloride, the metallic magnesium in which metallic nickel is dissolved can be floated above the magnesium chloride bath by allowing the molten magnesium chloride to stand. Focusing on this property, as one specific method, it is possible to reduce the concentration of metallic nickel in magnesium chloride by floating metallic magnesium in magnesium chloride and removing this metallic magnesium.

As a result, magnesium chloride having a low nickel content can be supplied to the electrolytic cell, and metallic magnesium having a low nickel content can be electrolytically produced. Therefore, metallic magnesium having a low nickel content can be supplied to the subsequent reduction step, and finally high-purity sponge titanium having a low nickel content can be manufactured.

(3) Method of removing magnesium metal in magnesium chloride Metal magnesium in magnesium chloride can be removed by various methods. Hereinafter, as a specific example thereof, a method for removing by static separation, filtration separation, and addition of titanium sponge particles will be described.

A. Static Separation As described above, the specific gravity of magnesium metal is smaller than that of magnesium chloride. Therefore, by allowing molten magnesium chloride to stand for a predetermined time, the magnesium metal mixed in magnesium chloride can be floated and separated.
Specifically, molten magnesium chloride produced as a by-product in the reduction step, which is a titanium production step by the Kroll method, is extracted into a container, and metallic magnesium liberated in the molten magnesium chloride is statically separated and removed. At this time, it is preferable to keep the entire container for holding the molten magnesium chloride at a temperature equal to or higher than the melting point of magnesium chloride, preferably in the range of 750 to 800 ° C. The higher the holding temperature, the more effective the separation of metallic magnesium is, but the above temperature range is preferable in consideration of economic efficiency.

As described above, the metallic magnesium present in magnesium chloride exists as droplets of various sizes, but since the specific gravity of metallic magnesium is smaller than that of magnesium chloride, the standing time elapses. As a result, metallic magnesium droplets float and separate on the magnesium chloride bath surface.

A preferable time for statically separating magnesium chloride necessary to keep the nickel content in the metal magnesium produced by electrolytically refining about 1000 kg of magnesium chloride to be 10 ppm or less is 10 to 300 minutes, and further. Is preferably 10 to 120 minutes. Among the magnesium metal droplets present in magnesium chloride,
The fine droplets remain in the magnesium chloride even if the above time is maintained, but the amount thereof is so small that it does not pose a practical problem.

In order to remove the bath from the magnesium chloride container, it is preferable to remove it from the bath or from the bottom of the bath in order to avoid mixing of the floated and separated metal magnesium. Alternatively, it is also effective to remove magnesium metal floated in magnesium chloride in advance and then withdraw magnesium chloride from the container.

Further, the material of the container for extracting the molten magnesium chloride from the reduction step, the container for holding the molten magnesium chloride and statically separating the metallic magnesium, and the container for extracting the molten magnesium chloride after the static separation of the metallic magnesium. In consideration of heat resistance, stainless steel or the like is usually used, but in order to avoid contamination with nickel or the like while holding it in the container, use a container of carbon steel on the inner surface side and stainless steel on the outer surface side. desirable. Further, it is desirable to use a container in which carbon steel on the inner surface side is welded by welding, or a container in which the outer surface side and the inner surface side are clad materials made of stainless steel and carbon steel.

B. Filtration-separated molten magnesium has the property of having a higher viscosity than magnesium chloride. Using this property,
For example, metallic magnesium can be efficiently removed by passing magnesium chloride containing metallic magnesium particles through a porous filter. A commercially available ceramic filter can be used as the filter, and the material thereof is preferably carbon, silicon nitride or the like.

C. Addition of titanium sponge particles Since the magnesium metal dispersed in magnesium chloride has a high viscosity as described above, it easily adheres to a solid. By taking advantage of this property, it is possible to adsorb and remove metallic magnesium present in the magnesium chloride bath by introducing titanium sponge particles into the magnesium chloride bath. The sponge titanium particles having a particle size of 5 to 20 mm are effective for adsorbing metallic magnesium.

If the particle size of titanium sponge particles is too small,
Although it does not float on the magnesium chloride bath and is brought into the electrolysis process, it is not preferable to bring sponge titanium particles into the electrolysis process. On the contrary, if it is too large, the residence time in the magnesium chloride bath is too short, and it becomes difficult to capture the metal magnesium. A sufficient effect can be obtained if the amount of titanium sponge added to the molten magnesium chloride bath is about 1 to 5 kg per 1000 kg of magnesium chloride.

The nickel content in the high-purity magnesium produced as described above is 10 ppm or less, preferably 5 ppm or less.

(4) Production of high-purity sponge titanium using low nickel metal magnesium In the method of producing high-purity titanium of the present invention, the high-purity metal magnesium produced by the above method is reacted with titanium tetrachloride. In this way, by using metallic magnesium having an extremely low nickel content as a reducing agent, sponge titanium having an extremely low nickel content is produced, and an electronic material which is reluctant to mix impurity metals such as nickel and iron and chromium. It is suitable for producing high-purity titanium for automobiles.

Further, titanium sponge having a lower nickel content can be manufactured by using a reducing container lined with carbon steel or mild steel having a low nickel content. Specifically, the inner surface side of the cylindrical portion is carbon steel, the outer surface side is stainless steel, and the carbon steel on the inner surface side is welded by welding, or the clad material made of stainless steel and carbon steel on the outer surface side and the inner surface side. Is preferred. Furthermore, a container in which the carbon content of carbon steel is 1.0 to 1.8 times the carbon content of stainless steel in the state before use is desirable.

By using a reducing container having stainless steel on the outer surface side and carbon steel on the inner surface side as described above, not only the impurity components such as nickel in the titanium sponge are reduced, but also the metal charged in the reduction reaction is used. It is possible to prevent dissolution of impurity components such as nickel in magnesium. At this time, metallic magnesium is similarly liberated in the magnesium chloride produced as a by-product during the reduction reaction, but the nickel content in the metallic magnesium becomes smaller.
After that, if the metallic magnesium is removed by the method of the present invention in the preceding stage and the electrolytic refining of magnesium chloride is performed, it becomes possible to produce highly pure metallic magnesium containing very few impurities such as nickel due to a synergistic effect.

Conventionally, it was possible to produce high-purity titanium having a nickel content of about several tens of ppm by using a reducing vessel lined with mild steel having a low nickel content, but the high-purity metallic magnesium obtained by the method of the present invention can be produced. When used in combination, the nickel content is several ppm, specifically 1 to 5 p
It is possible to produce high-purity sponge titanium having an extremely low pm.

[0026]

EXAMPLES Next, the present invention will be described in more detail by presenting more specific examples. [Example 1] 3000 kg of magnesium chloride by-produced in the reduction reaction in the titanium production process by the Kroll method was withdrawn into a container equipped with an extraction tube and allowed to stand for 30 minutes.
The inside of the container was pressurized to discharge magnesium chloride from the bottom of the container, and the magnesium chloride from which metallic magnesium was separated and removed was transferred to an electrolytic cell. Next, magnesium chloride in the electrolytic cell was electrolyzed to produce metallic magnesium. The nickel content in this metallic magnesium was 1.0 ppm.

[Example 2] 6000 kg of magnesium metal obtained in Example 1 was placed in a reducing container (made of stainless steel), and 15000 kg of titanium tetrachloride was continuously added to this to produce titanium sponge. The nickel content in this titanium sponge was 2 ppm.

[Comparative Example 1] After magnesium chloride was charged into a container, it was transferred to an electrolytic cell without performing a standing operation, and magnesium chloride was electrolyzed under the same conditions as in Example 1 to produce metallic magnesium. The nickel content in this metallic magnesium was 30 ppm.

[Comparative Example 2] Titanium sponge was produced in the same manner as in Example 1 except that the magnesium metal obtained in Comparative Example 1 was used. The nickel content in this titanium sponge was 300 ppm.

[0030]

As described above, according to the present invention,
After removing the magnesium metal present in the molten magnesium chloride by-produced in the reduction reaction of the titanium production process by the Kroll method, the magnesium chloride is electrolytically refined, so that high-purity metallic magnesium with less nickel contamination can be produced. It is possible to produce high-purity titanium with less nickel contamination by reacting the high-purity metallic magnesium with titanium tetrachloride using this metallic magnesium as a raw material.

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Claims (4)

[Claims] 1. A method for producing high-purity metallic magnesium, which comprises electrolytically refining the magnesium chloride after removing metallic magnesium present in magnesium chloride by-produced in the titanium production step by the Kroll method. 2. The method for producing high-purity metallic magnesium according to claim 1, wherein the nickel content in the metallic magnesium after the electrolytic refining is 10 ppm or less. 3. The molten magnesium chloride by-produced in the titanium production process by the Kroll method is extracted into a container, and the metallic magnesium liberated in the molten magnesium chloride is statically separated and removed. A method for producing the high-purity metallic magnesium described. 4. A method for producing high-purity titanium, which comprises reacting the high-purity metallic magnesium according to claim 1 or 2 with titanium tetrachloride.