JPS6160839A - Refining method refractory metal - Google Patents

Abstract

PURPOSE:To prevent a back flow of air to a device, and to suppress contamination of a product metal by leading in an inert gas and continuing heating in a negative pressure atmosphere, in the latter half period of a process for separating mixed Mg and MgCl2 by heating a Kroll process reaction product under a reduced pressure. CONSTITUTION:A reaction product 4 in which Mg and MgCl2 obtained by a Kroll process are mixed is contained in a reducing reaction vessel 5 of the lower part of a cylindrical body 3 provided in an electric heating furnace 2. After installing a vessel supporting frame, an empty reducing reaction vessel 11 is installed, and the upper part and the lower part of the cylindrical body 3 are joined. Subsequently, a vacuum is formed through an exhaust pipe 6 of the top part, the lower part of the cylindrical body 3 is heated to about 950-1,000 deg.C, and the upper part of the cylindrical body 3 is cooled by a water jacket 7. This state is held for a prescribed time, and when a degree of vacuum in the suction port becomes about 2X10<-2>Torr, a small quantity of Ar gas is supplied from a conduit extending to the bottom part along the lower part of the cylindrical body 3, a degree of vacuum in this position is held at about 2-5X10<-2>Torr, and a coagulum of Mg, MgCl2, etc. is adhered to the inside surface of the vessel 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for refining refractory metals, particularly T + CJa, Zr
The present invention relates to a method for separating and removing magnesium chloride and metallic magnesium from a reaction product obtained by a reduction method of a metal chloride such as Cl4 with molten magnesium (so-called Kroll method).

A method for heating and separating unreacted metallic magnesium and magnesium chloride from the metal produced by the Chlor method is to carry hlg and MgCL in a circulating flow of inert gas and take them out of the system. is also known (Japanese Patent Publication No. 43-29861), but a method using vacuum distillation is more commonly adopted.

In the former method, since the operation is carried out in a positive pressure Ar atmosphere, the evaporation rate of Mg and MgCIt is low, and the circulating gas carrying these substances is cooled, and solidified mari and MgClm are captured by a filter. It requires a complex equipment configuration. In addition, the collected ceramic and MgCl heavy particles adhere to the r-cloth, which requires time and effort to collect, and the recovered material is highly contaminated, making it difficult to reuse.

- In the vacuum distillation process, the entire system is evacuated with a vacuum tube and continuously heated to about 1000'C in the case of Ti, for example. From the spongy metal housed in the retort,
First, demon steam is generated, which is guided to a cooling section installed outside the retort and solidified. The pressure inside the retort during pigeon steam generation is relatively high (, several tens of rnfrLHglI
When c reaches Rukodo Moalca, most of the Mg evaporates and Q exhausts (and
When the time comes for MgCl2 vapor to be generated, the vapor pressure is one order of magnitude lower than that of 84 g, so the degree of vacuum within the device increases considerably, and the period is long. Therefore, if there is a defect in the airtightness of the device at this stage, the product will be contaminated by the intruding outside air pressure. The risk of such contamination is
It is extremely large when the metal manufactured by 'II has a strong affinity for oxygen and nitrogen, such as Ti and other refractory metals, and is used as a getter to obtain a high degree of vacuum.

Therefore, it is necessary to ensure a high degree of airtightness in equipment used in the vacuum distillation process, and for this reason, these equipments are usually tested for airtightness using pressurized gas prior to raising the temperature. However, in an actual device with a complicated configuration, this test requires a great deal of labor and time and is often impractical, and depending on the shape of the sealing material, it may not be possible to maintain the exhaust system at a high positive pressure state.

In this way, it is often difficult to completely check the airtightness of the entire system, and if a leak occurs after the vacuum distillation operation has started, the entire system is under reduced pressure, so it is difficult to find the leak location. It is extremely difficult to do this, and in the end, the traditional precision process of vacuum distillation has inevitably resulted in a certain degree of product contamination, resulting in a low yield of high-quality products.

Therefore, one of the main objectives of the present invention is to eliminate the drawbacks of both the above-mentioned prior art, the gist of which is to
A method for separating vaporized or liquefied ceramic and MgCJ from solid metal by heating a large metal lump mixed with , in a space separated from the outside air, at least
Refining of refractory metal characterized by introducing an inert gas flow into the space in the latter half of the separation process when the partial pressure of l2 is significantly reduced, and continuing heating under a negative inert gas atmosphere pressure. It's in the law.

When operating according to the method of the present invention, backflow of air from the connections and exhaust system of the distillation apparatus into the apparatus is prevented and contamination of product metals is minimized.

During the implementation of the method of the present invention, the metal ingot to be refined may be used, for example, in
Using a device such as that described in the above, the IC can be placed above or below the internal space of the distillation apparatus, and the lower or upper part can be used as a cooling section to solidify and adhere evaporated carbon dioxide and MgCI soda thereto. Alternatively, in order to perform Mg reduction of metal chlorides and distillation operations in the same apparatus, for example,
No. 5-56255, uSP 6,684.264] The devices described in each publication can be modified and used. When the reduction process is performed in a separate device, a double cylinder configuration using an inner cylinder is convenient for transporting the metal lump.

When carrying out the method of the present invention using the various devices described above,
Several further embodiments are available.

For example, regarding the point where inert gas is introduced (injected), the gas used has a small amount of fire, and there is almost no leakage from the retort body of the distillation equipment, so it is not possible to prevent the original purpose of preventing air from entering. It is sufficient that the inert gas is introduced (injected) on the same side of the metal mass to be purified as the vacuum suction side (for example, above the apparatus). In this case, it is a good start in that a device with a relatively basic structure can be obtained. On the other hand, if the gas is introduced on the side opposite to the suction, it is expected that the introduced airflow will transport the slag and MgCl2 to the cooling section, which will shorten the vacuum distillation time.
More preferred. At this time, the metal lump to be refined is
In the case of a vacuum distillation device configured to heat the container under a C, it is best to extend the pipe for introducing the inert gas along the container wall and place it in advance so that it has an opening near the bottom of the container. .

For example, when using a dedicated distillation retort with a heating section below and placing an inner cylinder containing metal inside the retort,
A conduit with an opening is provided at the bottom of the retort. In addition, when the reduction operation and the distillation operation are carried out using a common retort (for example, as described in JP-A-59-133335), the piping used for discharging the by-product MgCl2 during the reduction operation is It can be used as an inert gas introduction pipe. By doing this, the inert gas is sufficiently preheated by the heated furnace to K, 900"C or more, while passing through the inlet tube, and to prevent solidification of MgCl2 or ~1 g (a special No special equipment is required.

In order to simplify the structure, the opening of the inlet pipe can be provided in the lower part of the cooling section in the above device.

In this case, depending on the gas introduced, Mg and MgL: 11
The steam will be cooled to some extent, but since the amount of gas introduced is small, the steam will not solidify and fall.In fact, there will be a slight effect of promoting the solidification and adhesion of the steam to the cooling wall.

Furthermore, if the connection between the heating and retort parts and the cooling cylinder is completely airtight, the opening of the introduction pipe may be provided near the lid of the cooling cylinder. This also prevents exhaust gas from flowing back into the vacuum system due to leaks in the lid and vacuum system piping.

-10,000°C. For a vacuum separation apparatus 1c in which the metal to be refined is placed in the upper part and the lower part is used as a cooling section, the arrangement of the interstitial tubes can be reversed to the above cases.

In the method of the present invention, an inert gas is introduced at least after the vacuum separation operation, thereby reducing the degree of vacuum in the vacuum system to some extent, thereby preventing leakage that is impossible or difficult to detect in the airtightness test before the start of the operation. This prevents the VC refined metal from being contaminated during vacuum distillation by a small amount of air entering from the place. Therefore, the system can function satisfactorily with a small amount of gas. For example, throughout the distillation operation, a pressure of about I Torr should be maintained without continuing evacuation (Ar may be introduced, but to obtain a higher distillation rate, it is necessary to maintain a pressure of around I Torr), but to obtain a higher distillation rate, it is necessary to maintain a pressure of about I Torr, i.e. with less gas introduced. Generally, the ultimate vacuum level (
For example, it is preferable to introduce M gas so that the pressure (about 10-2 Torr) is maintained throughout the operation.

As described above, since the method of the present invention performs distillation operation at a relatively low degree of vacuum, it does not require a large-capacity high-vacuum bonder unlike distillation operations at a high degree of vacuum, so the exhaust system can be configured simply. Be able to do it. Furthermore, since the airtightness test before operation can be simplified, the time and labor required for this can be reduced.

In the method of the present invention, since the distillation operation is performed at a low vacuum level,
The efficiency of the vacuum separation operation itself is somewhat reduced due to the difference in vapor pressure from impurities, but on the other hand, the thermal conductivity increases due to the presence of gas in the system.1 The final impurity removal efficiency decreases. Few. In addition, since inert gas is constantly introduced into the system, even if there is a problem with the exhaust system and it becomes necessary to create positive pressure in the system, appropriate measures can be taken to prevent contamination of refined metals. It is possible to take prompt action, maintain high quality, and prevent a decline in yield despite these troubles.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows a longitudinal sectional view of a separation device suitable for carrying out the method of the invention. The lower part of the vacuum separator, shown as 1 in its entirety, is essentially a closed structure in which an electric heating furnace 2 connected to a suitable pressure reducing means (not shown) is disposed. A vertically elongated cylindrical body 6 is installed in the furnace 2, and a reduction reaction vessel 5 holding a reaction mixture 4 consisting of the produced metal -J-MgCl* obtained by the Kroll method is accommodated in the lower part of the cylinder.

The upper part of the cylinder 5, which can also protrude from the furnace 2, can be separated from the lower part placed in the furnace, and an exhaust pipe 6 for depressurization is installed at the top, and a water canopy 7 for cooling is installed around the top. An inert gas introduction pipe 8 extends from the bottom of the cylinder 3 overflowing the vessel wall, and has an opening at the bottom. A removable heat shield 9 is attached to the middle part of the cylinder. An empty reduction reaction container 11 is fixed to the lid 10 of the cylinder 3 with bolts, and the inner surface 1clV1g,
A coagulum such as MgCl is attached. An example using a device having such a configuration is as follows.

Example An electric furnace having an essentially cylindrical space with an inner diameter of 2 m and a depth of 4 m has an inner diameter of t6 m and a wall thickness of 32 IR(r) S U S
The lower part of the cylinder made of 516 is installed. Placed inside this was an outer diameter of 1.4 m, a wall thickness of 16 mm, a total length of 2.4 m,
Approximately 4 pieces of titanium sponge are used in the reaction vessel made of SUS A10.
A mixture containing tons and small amounts of MgC1- and Mg is retained.

After installing the support piece for the container, install an empty reduction reaction container of the same type as the VC placed at the bottom of the cylinder (with the bottom plate removed), then cover the top of the cylinder and connect it to the bottom. . A vacuum is drawn through the tube at the top, and the lower part of the cylinder is heated to 950°C in a furnace.
Heat to ~1000'C, then cool the top.

The temperature was maintained at the above temperature for 20 hours, and when the degree of vacuum at the suction port of the vacuum pump reached 2 x 10-'' Torr,
A small amount of Ar gas is supplied through a conduit extending along the lower part of the cylinder and opening at the bottom, and the degree of vacuum at the above position is reduced to 2.
~5×10-”J'orr K was maintained. This state was maintained for 72 hours to complete the separation operation.

The average analysis values of the entire titanium sponge mass obtained were as follows.

Oxygen s o o ppm Nitrogen 301)
I)m 120ppm Chlorine 250pI
Xn hardness: 80BHN This quality is almost the same as that obtained with a conventional completely airtight device, and no major difference was observed in the total operating time.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view schematically showing a vacuum separation apparatus suitable for carrying out the method of the present invention. 1... Separation device (whole); 2... Electric heating furnace; 3... Cylindrical body; 4... Reaction mixture; 5... Reduction reaction vessel; 6... Exhaust pipe; 7... Water mantle; 8... Gas introduction pipe; 9... Heat shield; 10... ...Lid; 1
1... Reduction reaction vessel.

Claims (1)

[Claims] 1. Mg that is vaporized or liquefied by heating a refractory metal lump mixed with Mg and MgCl_2 in a space separated from the outside air.
and MgCl_2 from a solid metal, at least in the latter half of the separation process when the partial pressures of Mg and MgCl_2 are significantly reduced, a stream of inert gas is introduced into the space, and an inert gas under negative pressure is introduced into the space. A method for refining refractory metals characterized by continuing heating in a gas atmosphere. 2. The method for refining a refractory metal according to claim 1, wherein the inert gas is a gas containing argon as a main component.